Patent Publication Number: US-9842128-B2

Title: Systems and methods for atomic storage operations

Description:
TECHNICAL FIELD 
     This disclosure relates to storage systems and, in particular, to systems and methods for maintaining file consistency. 
     SUMMARY 
     Disclosed herein are embodiments of a method for implementing atomic storage operations. Embodiments of the disclosed method may include linking transactional identifiers to target identifiers of an atomic storage request, redirecting storage operations of the atomic storage request to the transactional identifiers, and/or moving data of the redirected storage operations from the transactional identifiers to the target identifiers in response to completing the storage operations of the atomic storage request. 
     The storage operations may comprise appending data to a storage medium with metadata configured to associate the appended data with one or more of the transactional identifiers. Moving the appended data may comprise storing metadata on the storage medium configured to associate the appended data with the target identifiers. 
     The storage operations comprise storing data on a non-volatile storage medium with metadata configured to bind the stored data with one or more intermediate identifiers that are associated with respective transactional identifiers. Moving the stored data may comprise storing a persistent note on the non-volatile storage medium configured to bind the one or more intermediate identifiers to respective target identifiers. In some embodiments, the method further includes acknowledging completion of the atomic storage request in response to moving the data of the redirected storage operations. 
     Disclosed herein are embodiments of an apparatus for implementing atomic storage operations. The disclosed apparatus may comprise a redirection module configured to map a second set of identifiers to a first set of logical identifiers of a storage request, a log storage module configured to perform storage operations of the storage request on a storage device within the second set of identifiers, and/or an atomic storage module configured to move the storage operations of the storage request to the first set of logical identifiers. The atomic storage module may be configured to move the storage operations by storing persistent metadata to the storage device. The persistent metadata may be configured to bind data segments stored on the storage device in association with the second set of identifiers to the first set of identifiers. The atomic storage module may be further configured to acknowledge completion of the storage request in response to determining that the persistent metadata will be stored on the storage device. The first set of identifiers may comprise a plurality of disjoint sets of logical identifiers, and the persistent metadata may be a single persistent note configured to bind the data segments to respective logical identifiers within the plurality of disjoint sets of logical identifiers. 
     In some embodiments, the redirection module is configured to allocate the second set of identifiers within a different address space than an address space of the first set of identifiers. Alternatively, the redirection module may be configured to allocate the second set of identifiers within a designated region of an address space of the first set of identifiers. The second set of identifiers may correspond to a transactional address space, and the disclosed apparatus may further include a reconstruction module configured to invalidate data segments associated with identifiers of the transactional address space. 
     The atomic storage module may be configured to invalidate one of the identifiers within the first set of identifiers in response to moving a storage operation configured to invalidate data of one of the identifiers in the second set of identifiers. The log storage module may be configured to append data segments to an ordered log of data segments on the storage device. The log storage module may be further configured to append a data segment that does not pertain to the storage request between two or more data segments of the storage request within the ordered log of data segments. 
     Disclosed herein are embodiments of a system for implementing atomic storage operations. The system may include means for receiving an atomic storage request pertaining to a set of destination logical identifiers, means for linking a set of transactional identifiers to the destination set of logical identifiers, means for appending a plurality of data packets pertaining to the atomic storage request to a sequential storage log on a storage device, wherein the data packets comprise persistent metadata configured to associate the data packets with respective transactional identifiers, and/or means for appending a persistent note to the storage log, wherein the persistent note is configured to associate the plurality of data packets comprising persistent metadata configured to associate the data packets with respective transactional identifiers with respective destination logical identifiers. 
     The disclosed system may further include means for mapping logical identifiers of the set of destination logical identifiers to respective transactional identifiers. In some embodiments, the system includes means for binding one or more of the transactional identifiers to a storage location associated with a logical identifier that is linked to the respective one or more transactional identifiers. Embodiments of the disclosed system may further comprise means for providing access to the data packets comprising the persistent metadata configured to associate the data packets with respective transactional identifiers using respective designation logical identifiers in response to appending the persistent note. 
     The destination logical identifiers may correspond to a logical address space, and the transactional identifiers may correspond to a different, transactional address space. The system may further include means for reconstructing an index of mappings between logical identifiers of the logical address space and data packets on the storage device by use of persistent metadata of the data packets, and/or means for invalidating data packets associated with transactional identifiers corresponding to the different, transactional address space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a block diagram of one embodiment of a system for open-to-close consistency; 
         FIG. 1B  depicts embodiments of storage metadata; 
         FIG. 1C  is a block diagram depicting one embodiment of a storage array; 
         FIG. 1D  depicts one embodiment of a data packet format; 
         FIG. 1E  depicts one embodiment of a storage log; 
         FIG. 2  is a block diagram of another embodiment of a system for open-to-close consistency; 
         FIG. 3A  is a block diagram of one embodiment of a system comprising a storage layer configured to efficiently implement range clone, move, merge, and other higher-level storage operations; 
         FIG. 3B  depicts embodiments of range clone operations; 
         FIG. 3C  depicts further embodiments of range clone operations; 
         FIG. 3D  depicts further embodiments of range clone operations; 
         FIG. 3E  depicts further embodiments of range clone operations; 
         FIG. 4A  is a block diagram of another embodiment of a system for open-to-close consistency; 
         FIG. 4B  depicts embodiments of range clone operations implemented by use of a reference map; 
         FIG. 4C  depicts further embodiments of range clone operations implemented by use of a reference map; 
         FIG. 4D  depicts further embodiments of range clone operations implemented by use of a reference map; 
         FIG. 4E  depicts further embodiments of range clone operations implemented by use of a reference map; 
         FIG. 5A  is a block diagram of one embodiment of a system comprising an aggregation layer; 
         FIG. 5B  depicts embodiments of range clone operations implemented by use of an aggregation layer; 
         FIG. 6  depicts embodiments of deduplication operations; 
         FIG. 7  is a block diagram depicting one embodiment of a system comprising a storage layer configured to efficiently implement snapshot operations; 
         FIGS. 8A-E  depict embodiments of range move operations; 
         FIG. 9A  is a block diagram of a system comprising a storage layer configured to implement efficient file management operations; 
         FIG. 9B  depicts one embodiment of a storage layer configured to implement mmap checkpoints; 
         FIG. 9C  depicts embodiments of range clone and range merge operations implemented by a storage layer; 
         FIG. 9D  depicts further embodiments of range clone and range merge operations; 
         FIG. 9E  depicts further embodiments of range clone and range merge operations; 
         FIG. 9F  is a block diagram of one embodiment of a system comprising a storage layer configured to implement efficient open-to-close file consistency; 
         FIG. 9G  depicts further embodiments of close-to-open file consistency; 
         FIG. 10A  depicts one embodiment of a system comprising a storage layer configured to implement atomic storage operations; 
         FIG. 10B  depicts embodiments of atomic storage operations; 
         FIG. 11  is a flow diagram of one embodiment of a method for managing a logical interface of data storage in a contextual format on a non-volatile storage media; 
         FIG. 12  is a flow diagram of one embodiment of a method for managing a logical interface of contextual data; 
         FIG. 13  is a flow diagram of another embodiment of a method for managing a logical interface of contextual data; 
         FIG. 14  is a flow diagram of one embodiment of a method for managing range merge operations; 
         FIG. 15  is a flow diagram of another embodiment of a method for managing range clone operations; 
         FIG. 16  is a flow diagram of another embodiment of a method for managing range merge operations; 
         FIG. 17  is a flow diagram of one embodiment of a method atomic storage operations; 
         FIG. 18  is a flow diagram of another embodiment of a method for atomic storage operations; and 
         FIG. 19  is a flow diagram of another embodiment of a method for atomic storage operations. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is a block diagram of one embodiment of a computing system  100  comprising a storage layer  130  configured to provide storage services to one or more storage clients  106 . The storage layer  130  may be configured to provide open-to-close file services, as disclosed in further detail herein. The computing system  100  may comprise any suitable computing device, including, but not limited to, a server, desktop, laptop, embedded system, mobile device, and/or the like. In some embodiments, the computing system  100  may include multiple computing devices, such as a cluster of server computing devices. The computing system  100  may comprise processing resources  101 , volatile memory resources  102  (e.g., random access memory (RAM)), non-volatile storage resources  103 , and a communication interface  104 . The processing resources  101  may include, but are not limited to, general purpose central processing units (CPUs), application-specific integrated circuits (ASICs), and programmable logic elements, such as field programmable gate arrays (FPGAs), programmable logic arrays (PLGs), and the like. The non-volatile storage resources  103  may comprise a non-transitory machine-readable storage medium, such as a magnetic hard disk, solid-state storage medium, optical storage medium, and/or the like. The communication interface  104  may be configured to communicatively couple the computing system  100  to a network  105 . The network  105  may comprise any suitable communication network including, but not limited to, a Transmission Control Protocol/Internet Protocol (TCP/IP) network, a Local Area Network (LAN), a Wide Area Network (WAN), a Virtual Private Network (VPN), a Storage Area Network (SAN), a Public Switched Telephone Network (PSTN), the Internet, and/or the like. 
     The computing system  100  may comprise a storage layer  130 , which may be configured to provide storage services to one or more storage clients  106 . The storage clients  106  may include, but are not limited to, operating systems (including bare metal operating systems, guest operating systems, virtual machines, virtualization environments, and the like), file systems, database systems, remote storage clients (e.g., storage clients communicatively coupled to the computing system  100  and/or storage layer  130  through the network  105 ), and/or the like. 
     The storage layer  130  (and/or modules thereof) may be implemented in software, hardware, or a combination thereof. In some embodiments, portions of the storage layer  130  are embodied as executable instructions, such as computer program code, which may be stored on a persistent, non-transitory storage medium, such as the non-volatile storage resources  103 . The instructions and/or computer program code may be configured for execution by the processing resources  101 . Alternatively, or in addition, portions of the storage layer  130  may be embodied as machine components, such as general and/or application-specific components, programmable hardware, FPGAs, ASICs, hardware controllers, storage controllers, and/or the like. 
     The storage layer  130  may be configured to perform storage operations on a storage medium  140 . The storage medium  140  may comprise any storage medium capable of storing data persistently. As used herein, “persistent” data storage refers to storing information on a persistent, non-volatile storage medium. The storage medium  140  may include non-volatile storage media such as solid-state storage media in one or more solid-state storage devices or drives (SSD), hard disk drives (e.g., Integrated Drive Electronics (IDE) drives, Small Computer System Interface (SCSI) drives, Serial Attached SCSI (SAS) drives, Serial AT Attachment (SATA) drives, etc.), tape drives, writable optical drives (e.g., CD drives, DVD drives, Blu-ray drives, etc.), and/or the like. 
     In some embodiments, the storage medium  140  comprises non-volatile solid-state memory, which may include, but is not limited to, NAND flash memory, NOR flash memory, nano RAM (NRAM), magneto-resistive RAM (MRAM), phase change RAM (PRAM), Racetrack memory, Memristor memory, nanocrystal wire-based memory, silicon-oxide based sub-10 nanometer process memory, graphene memory, Silicon-Oxide-Nitride-Oxide-Silicon (SONOS), resistive random-access memory (RRAM), programmable metallization cell (PMC), conductive-bridging RAM (CBRAM), and/or the like. Although particular embodiments of the storage medium  140  are disclosed herein, the teachings of this disclosure could be applied to any suitable form of memory including both non-volatile and volatile forms. Accordingly, although particular embodiments of the storage layer  130  are disclosed in the context of non-volatile, solid-state storage devices  140 , the storage layer  130  may be used with other storage devices and/or storage media. 
     In some embodiments, the storage medium  140  includes volatile memory, which may include, but is not limited to, RAM, dynamic RAM (DRAM), static RAM (SRAM), synchronous dynamic RAM (SDRAM), etc. The storage medium  140  may correspond to memory of the processing resources  101 , such as a CPU cache (e.g., L1, L2, L3 cache, etc.), graphics memory, and/or the like. In some embodiments, the storage medium  140  is communicatively coupled to the storage layer  130  by use of an interconnect  127 . The interconnect  127  may include, but is not limited to, peripheral component interconnect (PCI), PCI express (PCI-e), serial advanced technology attachment (serial ATA or SATA), parallel ATA (PATA), small computer system interface (SCSI), IEEE 1394 (FireWire), Fiber Channel, universal serial bus (USB), and/or the like. Alternatively, the storage medium  140  may be a remote storage device that is communicatively coupled to the storage layer  130  through the network  105  (and/or other communication interface, such as a Storage Area Network (SAN), a Virtual Storage Area Network (VSAN), and/or the like). The interconnect  127  may, therefore, comprise a remote bus, such as a PCE-e bus, a network connection (e.g., Infiniband), a storage network, Fibre Channel Protocol (FCP) network, HyperSCSI, and/or the like. 
     The storage layer  130  may be configured to manage storage operations on the storage medium  140  by use of, inter alia, a storage controller  139 . The storage controller  139  may comprise software and/or hardware components including, but not limited to, one or more drivers and/or other software modules operating on the computing system  100 , such as storage drivers, I/O drivers, filter drivers, and/or the like; hardware components, such as hardware controllers, communication interfaces, and/or the like; and so on. The storage medium  140  may be embodied on a storage device  141 . Portions of the storage layer  130  (e.g., storage controller  139 ) may be implemented as hardware and/or software components (e.g., firmware) of the storage device  141 . 
     The storage controller  139  may be configured to implement storage operations at particular storage locations of the storage medium  140 . As used herein, a storage location refers to a unit of storage of a storage resource (e.g., a storage medium and/or device) that is capable of storing data persistently; storage locations may include, but are not limited to, pages, groups of pages (e.g., logical pages and/or offsets within a logical page), storage divisions (e.g., physical erase blocks, logical erase blocks, etc.), sectors, locations on a magnetic disk, battery-backed memory locations, and/or the like. The storage locations may be addressable within a storage address space  144  of the storage medium  140 . Storage addresses may correspond to physical addresses, media addresses, back-end addresses, address offsets, and/or the like. Storage addresses may correspond to any suitable storage address space  144 , storage addressing scheme, and/or arrangement of storage locations. 
     The storage layer  130  may comprise an interface  131  through which storage clients  106  may access storage services provided by the storage layer  130 . The storage interface  131  may include one or more of a block device interface, a virtualized storage interface, one or more virtual storage units (VSUs), an object storage interface, a database storage interface, and/or other suitable interface and/or an Application Programming Interface (API). 
     The storage layer  130  may provide for referencing storage resources through a front-end storage interface. As used herein, a “front-end storage interface” refers to an interface and/or namespace through which storage clients  106  may refer to storage resources of the storage layer  130 . A storage interface may correspond to a logical address space  132 . The logical address space  132  may comprise a group, set, collection, range, and/or extent of identifiers. As used herein, a “identifier” or “logical identifier” (LID) refers to an identifier for referencing a source resource; LIDs may include, but are not limited to, names (e.g., file names, distinguished names, and/or the like), data identifiers, references, links, LIDs, front-end identifiers, logical addresses, logical block addresses (LBAs), logical unit number (LUN) addresses, virtual unit number (VUN) addresses, virtual storage addresses, storage addresses, physical addresses, media addresses, back-end addresses, and/or the like. 
     The logical capacity of the logical address space  132  may correspond to the number of LIDs in the logical address space  132  and/or the size and/or granularity of the storage resources referenced by the LIDs. In some embodiments, the logical address space  132  may be “thinly provisioned.” As used herein, a thinly provisioned logical address space  132  refers to a logical address space  132  having a logical capacity that exceeds the physical storage capacity of the underlying storage resources (e.g., exceeds the storage capacity of the storage medium  140 ). In one embodiment, the storage layer  130  is configured to provide a 64-bit logical address space  132  (e.g., a logical address space comprising 2^26 unique LIDs), which may exceed the physical storage capacity of the storage medium  140 . The large, thinly-provisioned logical address space  132  may allow storage clients  106  to efficiently allocate and/or reference contiguous ranges of LIDs, while reducing the chance of naming conflicts. 
     The translation module  134  of the storage layer  130  may be configured to map LIDs of the logical address space  132  to storage resources (e.g., data stored within the storage address space  144  of the storage medium  140 ). The logical address space  132  may be independent of the back-end storage resources (e.g., the storage medium  140 ); accordingly, there may be no set or pre-determined mappings between LIDs of the logical address space  132  and the storage addresses of the storage address space  144 . In some embodiments, the logical address space  132  is sparse, thinly provisioned, and/or over-provisioned, such that the size of the logical address space  132  differs from the storage address space  144  of the storage medium  140 . 
     The storage layer  130  may be configured to maintain storage metadata  135  pertaining to storage operations performed on the storage medium  140 . The storage metadata  135  may include, but is not limited to, a forward map comprising any-to-any mappings between LIDs of the logical address space  132  and storage addresses within the storage address space  144 , a reverse map pertaining to the contents of storage locations of the storage medium  140 , validity bitmaps, reliability testing and/or status metadata, status information (e.g., error rate, retirement status, and so on), cache metadata, and/or the like. Portions of the storage metadata  135  may be maintained within the volatile memory resources  102  of the computing system  100 . Alternatively, or in addition, portions of the storage metadata  135  may be stored on non-volatile storage resources  103  and/or the storage medium  140 . 
       FIG. 1B  depicts one embodiment of any-to-any mappings  150  between LIDs of the logical address space  132  and back-end identifiers (e.g., storage addresses) within the storage address space  144 . The any-to-any mappings  150  may be maintained in one or more data structures of the storage metadata  135 . As illustrated in  FIG. 1B , the translation module  134  may be configured to map any storage resource identifier (any LID) to any back-end storage location. As further illustrated, the logical address space  132  may be sized differently than the underlying storage address space  144 . In the  FIG. 1B  embodiment, the logical address space  132  may be thinly provisioned, and, as such, may comprise a larger range of LIDs than the range of storage addresses in the storage address space  144 . 
     As disclosed above, storage clients  106  may reference storage resources through the LIDs of the logical address space  132 . Accordingly, the logical address space  132  may correspond to a logical interface  152  of the storage resources, and the mappings to particular storage addresses within the storage address space  144  may correspond to a back-end interface  154  of the storage resources. 
     The storage layer  130  may be configured to maintain the any-to-any mappings  150  between the logical interface  152  and back-end interface  154  in a forward map  160 . The forward map  160  may comprise any suitable data structure, including, but not limited to, an index, a map, a hash map, a hash table, a tree, a range-encoded tree, a b-tree, and/or the like. The forward map  160  may comprise entries  162  corresponding to LIDs that have been allocated for use to reference data stored on the storage medium  140 . The entries  162  of the forward map  160  may associate LIDs  164 A-D with respective storage addresses  166 A-D within the storage address space  144 . The forward map  160  may be sparsely populated, and as such, may omit entries corresponding to LIDs that are not currently allocated by a storage client  106  and/or are not currently in use to reference valid data stored on the storage medium  140 . In some embodiments, the forward map  160  comprises a range-encoded data structure, such that one or more of the entries  162  may correspond to a plurality of LIDs (e.g., a range, extent, and/or set of LIDs). In the  FIG. 1B  embodiment, the forward map  160  includes an entry  162  corresponding to a range of LIDs  164 A mapped to a corresponding range of storage addresses  166 A. The entries  162  may be indexed by LIDs. In the  FIG. 1B  embodiment, the entries  162  are arranged into a tree data structure by respective links. The disclosure is not limited in this regard, however, and could be adapted to use any suitable data structure and/or indexing mechanism. 
     Referring to  FIG. 1C , in some embodiments, the storage medium  140  may comprise a solid-state storage array  115  comprising a plurality of solid-state storage elements  116 A-Y. As used herein, a solid-state storage array (or storage array)  115  refers to a set of two or more independent columns  118 . A column  118  may comprise one or more solid-state storage elements  116 A-Y that are communicatively coupled to the storage layer  130  in parallel using, inter alia, the interconnect  127 . Rows  117  of the array  115  may comprise physical storage units of the respective columns  118  (solid-state storage elements  116 A-Y). As used herein, a solid-state storage element  116 A-Y includes, but is not limited to, solid-state storage resources embodied as a package, chip, die, plane, printed circuit board, and/or the like. The solid-state storage elements  116 A-Y comprising the array  115  may be capable of independent operation. Accordingly, a first one of the solid-state storage elements  116 A may be capable of performing a first storage operation while a second solid-state storage element  116 B performs a different storage operation. For example, the solid-state storage element  116 A may be configured to read data at a first physical address, while another solid-state storage element  116 B reads data at a different physical address. 
     A solid-state storage array  115  may also be referred to as a logical storage element (LSE). As disclosed in further detail herein, the solid-state storage array  115  may comprise logical storage units (rows  117 ). As used herein, a “logical storage unit” or row  117  refers to combination of two or more physical storage units, each physical storage unit on a respective column  118  of the array  115 . A logical erase block refers to a set of two or more physical erase blocks, a logical page refers to a set of two or more pages, and so on. In some embodiments, a logical erase block may comprise erase blocks within respective logical storage elements  115  and/or banks. Alternatively, a logical erase block may comprise erase blocks within a plurality of different arrays  115  and/or may span multiple banks of solid-state storage elements. 
     Referring back to  FIG. 1A , the storage layer  130  may further comprise a log storage module  136  configured to store data on the storage medium  140  in a log structured storage configuration (e.g., in a storage log). As used herein, a “storage log” or “log structure” refers to an ordered arrangement of data within the storage address space  144  of the storage medium  140 . Data in the storage log may comprise and/or be associated with persistent metadata. Accordingly, the storage layer  130  may be configured to store data in a contextual, self-describing format. As used herein, a contextual or self-describing format refers to a data format in which data is stored in association with persistent metadata. In some embodiments, the persistent metadata may be configured to identify the data, and as such, may comprise and/or reference the logical interface of the data (e.g., may comprise the LID(s) associated with the data). The persistent metadata may include other information, including, but not limited to, information pertaining to the owner of the data, access controls, data type, relative position or offset of the data, information pertaining to storage operation(s) associated with the data (e.g., atomic storage operations, transactions, and/or the like), log sequence information, data storage parameters (e.g., compression algorithm, encryption, etc.), and/or the like. 
       FIG. 1D  illustrates one embodiment of a contextual data format. The packet format  110  of  FIG. 1D  comprises a data segment  112  and persistent metadata  114 . The data segment  112  may be of any arbitrary length and/or size. The persistent metadata  114  may be embodied as one or more header fields of the data packet  110 . As disclosed above, the persistent metadata  114  may comprise the logical interface of the data segment  112 , and as such, may include the LID(s) associated with the data segment  112 . Although  FIG. 1D  depicts a packet format  110 , the disclosure is not limited in this regard and could associate data (e.g., data segment  112 ) with contextual metadata in other ways including, but not limited to, an index on the storage medium  140 , a storage division index, and/or the like. Data packets  110  may be associated with sequence information  113 . The sequence information may be used to determine the relative order of the data packets within the storage log. In some embodiments, data packets are appended sequentially within storage divisions of the storage medium  140 . The storage divisions may correspond to erase blocks, logical erase blocks, or the like. Each storage division may be capable of storing a large number of data packets  110 . The relative position of the data packets  110  within a storage division may determine the order of the packets within the storage log. The order of the storage divisions may be determined, inter alia, by storage division sequence information  113 . Storage divisions may be assigned respective sequence information  113  at the time the storage division is initialized for use (e.g., erased), programmed, closed, or the like. The storage division sequence information  113  may determine an ordered sequence of storage divisions within the storage address space  144 . Accordingly, the relative order of a data packet  110  within the storage log may be determined by: a) the relative position of the data packet  110  within a particular storage division and b) the order of the storage division relative to other storage divisions in the storage address space  144 . 
     In some embodiments, the storage layer  130  may be configured to manage an asymmetric, write-once storage medium  140 , such as a solid-state storage medium, flash storage medium, or the like. As used herein, a “write once” storage medium refers to a storage medium that is reinitialized (e.g., erased) each time new data is written or programmed thereon. As used herein, an “asymmetric” storage medium refers to a storage medium that has different latencies for different types of storage operations. In some embodiments, for example, read operations may be faster than write/program operations, and write/program operations may be much faster than erase operations (e.g., reading the media may be hundreds of times faster than erasing, and tens of times faster than programming the storage medium). The storage medium  140  may be partitioned into storage divisions that can be erased as a group (e.g., erase blocks). As such, modifying a single data segment “in-place” may require erasing the entire erase block comprising the data and rewriting the modified data to the erase block, along with the original, unchanged data. This may result in inefficient “write amplification,” which may excessively wear the media. In some embodiments, therefore, the storage layer  130  may be configured to write data “out-of-place.” As used herein, writing data “out-of-place” refers to updating and/or overwriting data at different storage location(s) rather than overwriting the data “in-place” (e.g., overwriting the original physical storage location of the data). Updating and/or overwriting data out-of-place may avoid write amplification, since existing, valid data on the erase block with the data to be modified need not be erased and recopied. Moreover, writing data out-of-place may remove erasure from the latency path of many storage operations, such that erasure latency is not part of the “critical path” of write operations. 
     The storage layer  130  may be configured to perform storage operations out-of-place by use of, inter alia, the log storage module  136 . The log storage module  136  may be configured to append data at a current append point within the storage address space  144  in a manner that maintains the relative order of storage operations performed by the storage layer  130 , forming a “storage log” on the storage medium  140 .  FIG. 1E  depicts one embodiment of append-only storage operations performed within the storage address space  144  of the storage medium  140 . As disclosed above, the storage address space  144  comprises a plurality of storage divisions  170 A-N (e.g., erase blocks, logical erase blocks, or the like), each of which can be initialized for use in storing data (e.g., erased). The storage divisions  170 A-N may comprise respective storage locations, which may correspond to pages, logical pages, and/or the like, as disclosed herein. The storage locations may be assigned respective storage addresses (e.g., storage address 0 to storage address N). 
     The log storage module  136  may be configured to store data sequentially from an append point  180  within the physical address space  144 . In the  FIG. 1E  embodiment, data may be appended at the append point  180  within storage location  182  of storage division  170 A and, when the storage location  182  is filled, the append point  180  may advance  181  to a next available storage location. As used herein, an “available” storage location refers to a storage location that has been initialized and has not yet been programmed (e.g., has been erased). As disclosed above, some types of storage media can only be reliably programmed once after erasure. Accordingly, an available storage location may refer to a storage location within a storage division  170 A-N that is in an initialized (or erased) state. 
     In the  FIG. 1E  embodiment, the logical erase block  170 B may be unavailable for storage due to, inter alia, not being in an erased state (e.g., comprising valid data), being out-of service due to high error rates, or the like. Therefore, after filling the storage location  182 , the log storage module  136  may skip the unavailable storage division  170 B, and advance the append point  180  to the next available storage division  170 C. The log storage module  136  may be configured to continue appending data to storage locations  183 - 185 , at which point the append point  180  continues at a next available storage division  170 A-N, as disclosed above. 
     After storing data on the “last” storage location within the storage address space  144  (e.g., storage location N  189  of storage division  170 N), the log storage module  136  may advance the append point  180  by wrapping back to the first storage division  170 A (or the next available storage division, if storage division  170 A is unavailable). Accordingly, the log storage module  136  may treat the storage address space  144  as a loop or cycle. 
     As disclosed above, sequentially appending data within the storage address space  144  may generate a storage log on the storage medium  140 . In the  FIG. 1E  embodiment, the storage log may comprise the ordered sequence of storage operations performed by sequentially storing data packets (and/or other data structures) from the append point  180  within the storage address space  144 . The append-only storage format may be used to modify and/or overwrite data out-of-place, as disclosed above. Performing storage operations out-of-place may avoid write amplification, since existing valid data on the storage divisions  170 A-N comprising the data that is being modified and/or overwritten need not be erased and/or recopied. Moreover, writing data out-of-place may remove erasure from the latency path of many storage operations (the erasure latency is no longer part of the “critical path” of a write operation). 
     In the  FIG. 1E  embodiment, a data segment X0 corresponding to LID A may be stored at storage location  191 . The data segment X0 may be stored in the self-describing packet format  110 , disclosed above. The data segment  112  of the packet  110  may comprise the data segment X0, and the persistent metadata  114  may comprise the LID (s) associated with the data segment (e.g., the LID A). A storage client  106  may request an operation to modify and/or overwrite the data associated with the LID A, which may comprise replacing the data segment X0 with data segment X1. The storage layer  130  may perform this operation out-of-place by appending a new packet  110  comprising the data segment X1 at a different storage location  193  on the storage medium  144 , rather than modifying the existing data packet  110 , in place, at storage location  191 . The storage operation may further comprise updating the storage metadata  135  to associate the LID A with the storage address of storage location  193  and/or to invalidate the obsolete data X0 at storage location  191 . As illustrated in  FIG. 1E , updating the storage metadata  135  may comprise updating an entry of the forward map  160  to associate the LID A  164 E with the storage address of the modified data segment X1. 
     Performing storage operations out-of-place (e.g., appending data to the storage log) may result in obsolete or invalid data remaining on the storage medium  140  (e.g., data that has been erased, modified, and/or overwritten out-of-place). As illustrated in  FIG. 1E , modifying the data of LID A by appending the data segment X1 to the storage log as opposed to overwriting and/or replacing the data segment X0 in place at storage location  191  results in keeping the obsolete version of the data segment X0 on the storage medium  140 . The obsolete version of the data segment X0 may not be immediately removed from the storage medium  140  (e.g., erased), since, as disclosed above, erasing the data segment X0 may involve erasing an entire storage division  170 A and/or relocating valid data on the storage division  170 A, which is a time-consuming operation and may result in write amplification. Similarly, data that is no longer is use (e.g., deleted or subject to a TRIM operation) may not be immediately removed. As such, over time, the storage medium  140  may accumulate a significant amount of “invalid” data. 
     The storage layer  130  may identify invalid data, such as the data segment X0 at storage location  191 , by use of the storage metadata  135  (e.g., the forward map  160 ). The storage layer  130  may determine that storage locations that are not associated with valid identifiers (LIDs) in the forward map  160  comprise data that does not need to be retained on the storage medium  140 . Alternatively, or in addition, the storage layer  130  may maintain other storage metadata  135 , such as validity bitmaps, reverse maps, and/or the like to efficiently identify data that has been deleted, has been TRIMed, is obsolete, and/or is otherwise invalid. 
     The storage layer  130  may be configured to reclaim storage resources occupied by invalid data. The storage layer  130  may be further configured to perform other media management operations including, but not limited to, refreshing data stored on the storage medium  140  (to prevent error conditions due to data degradation, write disturb, read disturb, and/or the like), monitoring media reliability conditions, and/or the like. As used herein, reclaiming a storage resource, such as a storage division  170 A-N, refers to erasing the storage division  170 A-N so that new data may be stored/programmed thereon. Reclaiming a storage division  170 A-N may comprise relocating valid data on the storage division  170 A-N to a new storage location. The storage layer  130  may identify storage divisions  170 A-N for reclamation based upon one or more factors, which may include, but are not limited to, the amount of invalid data in the storage division  170 A-N, the amount of valid data in the storage division  170 A-N, wear levels (e.g., number of program/erase cycles), time since the storage division  170 A-N was programmed or refreshed, and so on. 
     The storage layer  130  may be configured to reconstruct the storage metadata  135 , including the forward map  160 , by use of contents of the storage log on the storage medium  140 . In the  FIG. 1E  embodiment, the current version of the data associated with LID A may be determined based on the relative log order of the data packets  110  at storage locations  191  and  193 , respectively. Since the data packet at storage location  193  is ordered after the data packet at storage location  191  in the storage log, the storage layer  130  may determine that storage location  193  comprises the most recent, up-to-date version of the data corresponding to LID A. The storage layer  130  may reconstruct the forward map  160  to associate the LID A with the data packet at storage location  193  (rather than the obsolete data at storage location  191 ). 
       FIG. 2  depicts another embodiment of a system  200  comprising a storage layer  130 . The storage medium  140  may comprise a plurality of independent banks  119 A-N, each of which may comprise one or more storage arrays  115 A-N. Each independent bank  119 A-N may be coupled to the storage controller  139  via the interconnect  127 . 
     The storage controller  139  may comprise a storage request receiver module  231  configured to receive storage requests from the storage layer  130  via a bus  127 . The storage request receiver  231  may be further configured to transfer data to/from the storage layer  130  and/or storage clients  106 . Accordingly, the storage request receiver module  231  may comprise one or more direct memory access (DMA) modules, remote DMA modules, bus controllers, bridges, buffers, and so on. 
     The storage controller  139  may comprise a write module  240  that is configured to store data on the storage medium  140  in response to requests received via the request module  231 . The storage requests may comprise and/or reference the logical interface of the data pertaining to the requests. The write module  240  may be configured to store the data in a self-describing storage log, which, as disclosed above, may comprise appending data packets  110  sequentially within the storage address space  144  of the storage medium  140 . The data packets  110  may comprise and/or reference the logical interface of the data (e.g., may comprise the LID(s) associated with the data). The write module  240  may comprise a write processing module  242  configured to process data for storage. Processing data for storage may comprise one or more of: a) compression processing, b) encryption processing, c) encapsulating data into respective data packets  110  (and/or other containers), d) performing error-correcting code (ECC) processing, and so on. The write buffer  244  may be configured to buffer data for storage on the storage medium  140 . In some embodiments, the write buffer  244  may comprise one or more synchronization buffers configured to synchronize a clock domain of the storage controller  139  with a clock domain of the storage medium  140  (and/or interconnect  127 ). 
     The log storage module  136  may be configured to select storage location(s) for data storage operations and may provide addressing and/or control information to the storage arrays  115 A-N of the independent banks  119 A-N. As disclosed herein, the log storage module  136  may be configured to append data sequentially in a log format within the storage address space  144  of the storage medium  140 . 
     Storage operations to write data may comprise: a) appending one or more data packets to the storage log on the storage medium  140  and b) updating storage metadata  135  to associate LID(s) of the data with the storage addresses of the one or more data packets. In some embodiments, the storage metadata  135  may be maintained on memory resources of the storage controller  139  (e.g., on dedicated volatile memory resources of the storage device  141  comprising the storage medium  140 ). Alternatively, or in addition, portions of the storage metadata  135  may be maintained within the storage layer  130  (e.g., on a volatile memory  112  of the computing device  110  of  FIG. 1A ). In some embodiments, the storage metadata  135  may be maintained in a volatile memory by the storage layer  130 , and may be periodically stored on the storage medium  140 . 
     The storage controller  139  may further comprise a data read module  241  configured to read data from the storage log on the storage medium  140  in response to requests received via the storage request receiver module  231 . The requests may comprise LID(s) of the requested data, a storage address of the requested data, and/or the like. The read module  241  may be configured to: a) determine the storage address(es) of the data packet(s)  110  comprising the requested data by use of, inter alia, the forward map  160 , b) read the data packet(s)  110  from the determined storage address(es) on the storage medium  140 , and c) processing data for use by the requesting entity. Data read from the storage medium  140  may stream into the read module  241  via the read buffer  245 . The read buffer  245  may comprise one or more read synchronization buffers for clock domain synchronization, as described above. The read processing module  243  may be configured to processes data read from the storage medium  144 , which may include, but is not limited to, one or more of: a) decompression processing, b) decryption processing, c) extracting data from one or more data packet(s)  110  (and/or other containers), d) performing ECC processing, and so on. 
     The storage controller  139  may further comprise a bank controller  252  configured to selectively route data and/or commands of the write module  240  and/or read module  241  to/from particular independent banks  119 A-N. In some embodiments, the storage controller  139  is configured to interleave storage operations between the independent banks  119 A-N. The storage controller  139  may, for example, read from the storage array  115 A of bank  119 A into the read module  241  while data from the write module  240  is being programmed to the storage array  115 B of bank  119 B. Further embodiments of multi-bank storage operations are disclosed in U.S. patent application Ser. No. 11/952,095, entitled, “Apparatus, System, and Method for Managing Commands for Solid-State Storage Using Bank Interleave,” filed Dec. 12, 2006 for David Flynn et al., which is hereby incorporated by reference. 
     The write processing module  242  may be configured to encode data packets  110  into ECC codewords. As used herein, an ECC codeword refers to data and corresponding error detection and/or correction information. The write processing module  242  may be configured to implement any suitable ECC algorithm and/or generate ECC codewords of any suitable type, which may include, but are not limited to, data segments and corresponding ECC syndromes, ECC symbols, ECC chunks, and/or other structured and/or unstructured ECC information. ECC codewords may comprise any suitable error-correcting encoding, including, but not limited to, block ECC encoding, convolutional ECC encoding, Low-Density Parity-Check (LDPC) encoding, Gallager encoding, Reed-Solomon encoding, Hamming codes, Multidimensional parity encoding, cyclic error-correcting codes, BCH codes, and/or the like. The write processing module  242  may be configured to generate ECC codewords of a pre-determined size. Accordingly, a single packet may be encoded into a plurality of different ECC codewords and/or a single ECC codeword may comprise portions of two or more packets. Alternatively, the write processing module  242  may be configured to generate arbitrarily sized ECC codewords. Further embodiments of error-correcting code processing are disclosed in U.S. patent application Ser. No. 13/830,652, entitled, “Systems and Methods for Adaptive Error-Correction Coding,” filed Mar. 14, 2013 for Jeremy Fillingim et al., which is hereby incorporated by reference. 
     In some embodiments, the storage layer  130  leverages the logical address space  132  to efficiently implement high-level storage operations. The storage layer  130  may be configured to implement “clone” or “logical copy” operations. As used herein, a “clone” or “logical copy” refers to operations to efficiently copy or replicate data managed by the storage layer  130 . A clone operation may comprise creating a set of “cloned” LIDs that correspond to the same data as a set of “original” LIDs. A clone operation may, therefore, comprise referencing the same set of storage locations using two (or more) different logical interfaces (e.g., different sets of LIDs). A clone operation may, therefore, modify the logical interface of one or more data packets  110  stored on the storage medium  140 . A “logical move” may refer to an operation to modify the logical interface of data managed by the storage layer  130 . A logical move operation may comprise changing the LIDs used to reference data stored on the storage medium  140 . A “merge” operation may comprise merging different portions of the logical address space  132 . As disclosed in further detail herein, clone and/or move operations may be used to efficiently implement higher-level storage operations, such as deduplication, snapshots, logical copies, atomic operations, transactions, and/or the like. 
     Referring to  FIG. 3A , the storage layer  130  may comprise a logical interface management module  334  that is configured to manage logical interface operations pertaining to data managed by the storage layer  130 , such as clone operations, move operations, merge operations, and so on. Cloning LIDs may comprise modifying the logical interface of data stored in the storage medium  140  in order to, inter alia, allow the data to be referenced by use of two or more different sets of LIDs. Accordingly, creating a clone may comprise: a) allocating a set of LIDs in the logical address space  132  (or dedicated portion thereof) and b) associating the allocated LIDs with the same storage location(s) as an “original” set of LIDs by use of, inter alia, the storage metadata  135 . Creating a clone may, therefore, comprise adding one or more entries to a forward map  160  configured to associate the new set of cloned LIDs with a particular set of storage locations. 
     The logical interface management module  334  may be configured to implement clone operations according to a clone synchronization policy. A clone synchronization policy may be used to determine how operations performed in reference to a first one of a plurality of clones or copies is propagated to the other clones or copies. For example, clones may be synchronized with respect to allocation operations, such that a request to expand one of the clones comprises expanding the other clones and/or copies. As used herein, expanding a file (or other data segment) refers to increasing a size, range, and/or extent of the file, which may include adding one or more logical identifiers to the clone, modifying one or more of the logical identifiers allocated to the clone, and/or the like. The clone synchronization policy may comprise a merge policy, which may, inter alia, determine how differences between clones are managed when the clones are combined in a merge and/or fold operation (disclosed in additional detail below). 
       FIG. 3A  depicts one embodiment of a range clone operation implemented by the storage layer  130 . The range clone operation of  FIG. 3A  may be implemented in response to a request from a storage client  106 . In some embodiments, the interface  131  of the storage layer  130  may be configured to provide interfaces and/or APIs for performing clone operations. Alternatively, or in addition, the range clone operation may be performed as part of a higher-level operation, such as an atomic operation, transaction, snapshot, logical copy, file management operation, and/or the like. 
     As illustrated in  FIG. 3A , the forward map  160  of the storage layer  130  comprises an entry  362  configured to bind the LIDs  1024 - 2048  to media storage locations  3453 - 4477 . Other entries are omitted from  FIG. 3A  to avoid obscuring the details of the depicted embodiment. As disclosed herein, the entry  362 , and the bindings thereof, may define a logical interface  311 A through which storage clients  106  may reference the corresponding data (e.g., data segment  312 ); storage clients  106  may access and/or reference the data segment  312  (and/or portions thereof) through the storage layer  130  by use of the LIDs  1024 - 2048 . Accordingly, the LIDs  1024 - 2048  define, inter alia, the logical interface  311 A of the data segment  312 . 
     As disclosed herein, the storage layer  130  may be configured to store data in a contextual format on a storage medium  140  (e.g., packet format  110 ). In the  FIG. 3A  embodiment, the data packet  310  at storage locations  3453 - 4477  comprises a data segment  312 . The data packet  310  further includes persistent metadata  314  that indicates the logical interface of the data segment  312  (e.g., associates the data segment  312  with LIDs  1024 - 2048 ). As disclosed above, storing data in association with descriptive, persistent metadata may enable the storage layer  130  to rebuild the forward map  160  (and/or other storage metadata  135 ) from the contents of the storage log. In the  FIG. 3A  embodiment, the entry  362  may be reconstructed by associating the data stored at storage addresses  3453 - 4477  with the LIDs  1024 - 2048  referenced by the persistent metadata  314  of the packet  310 . Although  FIG. 3A  depicts a single packet  310 , the disclosure is not limited in this regard. In some embodiments, the data of the entry  362  may be stored in multiple, different packets  310 , each comprising respective persistent metadata  314  (e.g., a separate packet for each storage location, etc.). 
     The logical interface management module  334  may be configured to clone the entry  362  by, inter alia, allocating a new set of LIDs corresponding to the original LIDs to be cloned and binding the new LIDs to the storage locations of the original, source LIDs. As illustrated in  FIG. 3B , creating the clone of the LIDs  1024 - 2048  may comprise the logical interface management module  334  allocating an equivalent set of LIDs  6144 - 7168  and binding the cloned set of identifiers to the storage addresses  3453 - 4477 . Creating the clone may, therefore, comprise modifying the storage metadata  135  to expand the logical interface  311 B of the data segment  312  to include LIDs  6144 - 7168  without requiring the underlying data segment  312  to be copied and/or replicated on the storage media  140 . 
     The modified logical interface  311 B of the data segment  312  may be inconsistent with the contextual format of the corresponding data packet  310  stored at storage locations  3453 - 4477 . As disclosed above, the persistent metadata  314  of the data packet  310  references LIDs  1024 - 2048 , but does not include and/or reference the cloned LIDs  6144 - 7168 . The contextual format of the data segment  312  may be updated to be consistent with the modified logical interface  311 B (e.g., updated to associate the data with LIDs  1024 - 2048  and  6144 - 7168 , as opposed to only LIDs  1024 - 2048 ), which may comprise rewriting the data segment in a packet format that associates the data segment with both sets of LIDs. If the storage device  141  is a random-access, write-in-place storage device, the persistent metadata  314  may be updated in place. In other embodiments comprising a write-once, asymmetric storage medium  140 , such in-place updates may be inefficient. Therefore, the storage layer  130  may be configured to maintain the data in the inconsistent contextual format until the data is relocated in a media management operation, such as storage recovery, relocation, and/or the like (by the media management module  370 ). Updating the contextual format of the data segment  312  may comprise relocating and/or rewriting the data segment  312  on the storage medium  140 , which may be a time-consuming process and may be particularly inefficient if the data segment  312  is large and/or the clone comprises a large number of LIDs. Therefore, in some embodiments, the storage layer  130  may defer updating the contextual format of cloned data segment  312  and/or may update the contextual format in one or more background operations. In the meantime, the storage layer  130  may be configured to provide access to the data segment  312  while stored in the inconsistent contextual format (data packet  310 ). 
     The storage layer  130  may be configured to acknowledge completion of clone operations before the contextual format of the corresponding data segment  312  is updated. The data may be subsequently rewritten (e.g., relocated) in the updated contextual format on the storage medium  140 . The update may occur outside of the “critical path” of the clone operation and/or other foreground storage operations. In some embodiments, the data segment  312  is relocated by the media management module  370  as part of one or more of a storage recovery process, data refresh operation, and/or the like. Accordingly, storage clients  106  may be able to access the data segment  312  through the modified logical interface  311 B (e.g., in reference to LIDs  1024 - 2048  and/or  6144 - 7168 ) without waiting for the contextual format of the data segment  312  to be updated in accordance with the modified logical interface  311 B. 
     Until the contextual format of the data segment  312  is updated on the storage medium  140 , the modified logical interface  311 B of the data segment  312  may exist only in the storage metadata  135  (e.g., map  160 ). Therefore, if the forward map  160  is lost due to, inter alia, power failure or data corruption, the clone operation may not be reflected in the reconstructed storage metadata  135  (the clone operation may not be persistent and/or crash safe). As illustrated above, the persistent metadata  314  of the data packet  310  indicates that the data segment  312  is associated only with LIDs  1024 - 2048 , not  6144 - 7168 . Therefore, only entry  362  will be reconstructed (as in  FIG. 3A ), and entry  364  will be omitted; as a result, subsequent attempts to access the data segment  312  through the modified logical interface  311 B (e.g., through  6144 - 7168 ) may fail. 
     In some embodiments, the clone operation may further comprise storing a persistent note on the storage medium  140  to make a clone operation persistent and/or crash safe. As used herein, a “persistent note” refers to metadata stored on the storage medium  140 . Persistent notes  366  may correspond to a log order and/or may be stored in a packet format, as disclosed herein. The persistent note  366  may comprise an indication of the modified logical interface  311 B of the data segment  312 . In the  FIG. 3B  embodiment, the persistent note  366  corresponding to the depicted clone operation may be configured to associate the data stored at storage addresses  3453 - 4477  with both ranges of LIDs  1024 - 2048  and  6144 - 7168 . During reconstruction of the forward map  160  from the contents of the storage medium  140 , the persistent note  366  may be used to reconstruct both entries  362  and  364 , to associate the data segment  312  with both LID ranges of the updated logical interface  311 B. In some embodiments, the storage layer  130  may acknowledge completion of the clone operation in response to updating the storage metadata  135  (e.g., creating the entry  364 ) and storing the persistent note  366  on the storage medium  140 . The persistent note  366  may be invalidated and/or marked for removal from the storage medium  140  in response, updating the contextual format of the data segment  312  to be consistent with the updated logical interface  311 B (e.g., relocating and/or rewriting the data segment  312 , as disclosed above). 
     In some embodiments, the updated contextual format of the data segment  312  may comprise associating the data segment  312  with both LID ranges  1024 - 2048  and  6144 - 7168 .  FIG. 3C  depicts one embodiment of an updated contextual format (data packet  320 ) for the data segment  312 . As illustrated in  FIG. 3C , the persistent metadata  324  of the data packet  320  associates the data segment  312  with both LID ranges  1024 - 2048  and  6144 - 7168  of the updated logical interface  311 B. The data packet  320  may be written out-of-place, at different storage addresses ( 64432 - 65456 ) than the original data packet  310 , which may be reflected in updated entries  362  and  364  of the forward map  160 . In response to appending the data packet  320  to the storage log, the corresponding persistent note  366  (if any) may be invalidated (removed and/or marked for subsequent removal from the storage medium  140 ). In some embodiments, removing the persistent note  366  may comprise issuing one or more TRIM messages indicating that the persistent note  366  no longer needs to be retained on the storage medium  140 . Alternatively, or in addition, portions of the forward map  160  may be stored in a persistent, crash safe storage location (e.g., non-transitory storage resources  103  and/or the storage medium  140 ). In response to persisting the forward map  160  (e.g., the entries  362  and  364 ), the persistent note  366  may be invalidated, as disclosed above, even if the data segment  312  has not yet been rewritten in an updated contextual format. 
     The logical interface management module  334  may be configured to implement clone operations according to one or more different modes, including a “copy-on-write mode.”  FIG. 3D  depicts one embodiment of a storage operation performed within a cloned range in a copy-on-write mode. In a copy-on-write mode, storage operations that occur after creating a clone may cause the clones to diverge from one another (e.g., the entries  362  and  364  may refer to different storage addresses, ranges, and/or extents). In the  FIG. 3D  embodiment, the storage layer  130  has written the data segment  312  in the updated contextual data format (packet  320 ) that is configured to associate the data segment  312  with both LID ranges  1024 - 2048  and  6144 - 7168  (as depicted in  FIG. 3C ). A storage client  106  may then issue one or more storage requests to modify and/or overwrite data corresponding to the LIDs  6657 - 7168 . In the  FIG. 3D  embodiment, the storage request comprises modifying and/or overwriting data of the LIDs  6657 - 7168 . In response, the storage layer  130  may store the new and/or modified data on the storage medium  130 , which may comprise appending a new data packet  340  to the storage log, as disclosed above. The data packet  340  may associate the data segment  342  with the LIDs  6657 - 7424  (e.g., by use of persistent metadata  344  of the packet  340 ). The forward map  160  may be updated to associate the LIDs  6657 - 7424  with the data segment  342 , which may comprise splitting the entry  364  into an entry  365  configured to continue to reference the unmodified portion of the data in the data segment  312  and an entry  367  that references the new data segment  342  stored at storage addresses  78512 - 79024 . In the copy-on-write mode depicted in  FIG. 3D , the entry  362  corresponding to the LIDs  1024 - 2048  may be unchanged, and continue to reference the data segment  312  at storage addresses  64432 - 65456 . Although not depicted in  FIG. 3D , modifications within the range  1024 - 2048  may result in similar diverging changes affecting the entry  362 . Moreover, the storage request(s) are not limited to modifying and/or overwriting data. Other operations may comprise expanding the set of LIDs (appending data), removing LIDs (deleting, truncating, and/or trimming data), and/or the like. 
     In some embodiments, the storage layer  130  may support other clone modes, such as a “synchronized clone” mode. In a synchronized clone mode, changes made within a cloned range of LIDs may be reflected in one or more other, corresponding ranges. In the  FIG. 3D  embodiment, implementing the described storage operation in a “synchronized clone” mode may comprise updating the entry  362  to reference the new data segment  342 , as disclosed herein, which may comprise, inter alia, splitting the entry  362  into an entry configured to associate LIDs  1024 - 1536  with portions of the original data segment  312  and adding an entry configured to associate the LIDs  1537 - 2048  with the new data segment  342 . 
     Referring back to the copy-on-write embodiment of  FIG. 3D , the logical interface management module  334  may be further configured to manage clone merge operations. As used herein, a “merge” or “clone merge” refers to an operation to combine two or more different sets and/or ranges of LIDs. In the  FIG. 3D  embodiment, a range merge operation may comprise merging the entry  362  with the corresponding cloned entries  365  and  367 . The logical interface management module  334  may be configured to implement range merge operations according to a merge policy, such as: a write-order policy in which more recent changes override earlier changes; a priority-based policy based on the relative priority of storage operations (e.g., based on properties of the storage client(s)  106 , applications, and/or users associated with the storage operations); a completion indicator (e.g., completion of an atomic storage operation, failure of an atomic storage operation, or the like); fadvise parameters; ioctrl parameters; and/or the like. 
       FIG. 3E  depicts one embodiment of a range merge operation. The range merge operation of  FIG. 3E  may comprise merging the range  6144 - 6656  into the range  1024 - 2048 . Accordingly, the range merge operation may comprise selectively applying changes made within the LID range  6144 - 6656  to the LID range  1024 - 2048  in accordance with the merge policy. The range merge operation may, therefore, comprise updating the LID range  1024 - 2048  to associate LIDs  1537 - 2048  with the storage addresses  78512 - 79024  comprising the new/modified data segment  342 . The update may comprise splitting the entry  362  in the forward map  160 ; the entry  372  may be configured to associate the LIDs  1024 - 1536  with portions of the original data segment  312 , and entry  373  may be configured to associate LIDs  1537 - 2048  with the new data segment  342 . Portions of the data segment  312  that are no longer referenced by the LIDs  1537 - 2048  may be invalidated, as disclosed herein. The LID range  6144 - 7168  that was merged into the original, source range may be deallocated and/or removed from the forward map  160 . 
     The range merge operation illustrated in  FIG. 3E  may result in modifying the logical interface  311 C to portions of the data. The contextual format of the data segment  342  (the data packet  340 ) may associate the data segment  342  with LIDs  6657 - 7168 , rather than the merged LIDs  1537 - 2048 . As disclosed above, the storage layer  130  may provide access to the data segment  342  stored in the inconsistent contextual format. The storage layer  130  may be configured to store the data segment  342  in an updated contextual format, in which the data segment  342  is associated with the LIDs  1537 - 2048  in one or more background operations (e.g., storage recovery operations). In some embodiments, the range merge operation may further comprise storing a persistent note  366  on the storage medium  140  to associate the data segment  342  with the updated logical interface  311 C (e.g., associate the data segment  342  at storage addresses  78512 - 79024  with the LIDs  1537 - 2048 ). As disclosed above, the persistent note  366  may be used to ensure that the range merge operation is persistent and crash safe. The persistent note  366  may be removed in response to relocating the data segment  342  in a contextual format that is consistent with the logical interface  311 C (e.g., associates the data segment  342  with the LIDs  1537 - 2048 ), persisting the forward map  160 , and/or the like. 
     The clone operations disclosed in conjunction with  FIGS. 3A-E  may be used to implement other logical operations, such as a range move operation. Referring back to  FIGS. 3A-C , a clone operation to replicate entry  362  of the forward map  160  may comprise modifying the logical interface associated with the data segment  312  to associate the data segment  312  with both the original set of LIDs  1024 - 2048  and a new set of cloned LIDs  6144 - 7168  (of entry  364 ). The clone operation may further include storing a persistent note  366  indicating the updated logical interface  311 B of the data segment  312  and/or rewriting the data segment  312  in accordance with the updated logical interface  311 B in one or more background storage operations. 
     The logical interface management module  334  may be further configured to implement “range move” operations. As used herein, a “range move” operation refers to modifying the logical interface of one or more data segments to associate the data segments with different sets of LIDs. A range move operation may, therefore, comprise updating storage metadata  135  (e.g., the forward map  160 ) to associate the one or more data segments with the updated logical interface, storing a persistent note  366  on the storage medium  140  indicating the updated logical interface of the data segments, and rewriting the data segments in a contextual format (packet format  310 ) that is consistent with the updated logical interface, as disclosed herein. Accordingly, the storage layer  130  may implement range move operations using the same mechanisms and/or processing steps as those disclosed above in conjunction with  FIGS. 3A-E . 
     The clone and/or range move operations disclosed in  FIGS. 3A-E  may impose certain limitations on the storage layer  130 . As disclosed above, storing data in a contextual format may comprise associating the data with each LID that references the data. In the  FIG. 3C  embodiment, the persistent metadata  324  comprises references to both LID ranges  1024 - 2048  and  6144 - 7168 . Increasing the number references to a data segment may, therefore, impose a corresponding increase in the overhead of the contextual data format (e.g., increase the size of the persistent metadata  324 ). In some embodiments, the size of the persistent metadata  314  may be limited, which may limit the number of references and/or clones that can reference a particular data segment  312 . Moreover, inclusion of multiple references to different LID (s) may complicate storage recovery operations. The number of forward map entries that need to be updated when a data segment  312  is relocated may vary in accordance with the number of LIDs that reference the data segment  312 . Referring back to  FIG. 3C , relocating the data segment  312  in a grooming and/or storage recovery operation may comprise updating two separate entries  362  and  364 . Relocating a data segment referenced by N different LIDs (e.g., N different clones) may comprise updating N different entries in the forward map  160 . Similarly, storing the data segment may comprise writing N entries into the persistent metadata  314 . This variable overhead may reduce the performance of background storage recovery operations and may limit the number of concurrent clones and/or references that can be supported. 
     In some embodiments, the logical interface management module  334  may comprise and/or leverage an intermediate mapping layer to reduce the overhead imposed by clone operations. The intermediate mapping layer may comprise “reference entries” configured to facilitate efficient cloning operations (as well as other operations, as disclosed in further detail herein). As used herein, a “reference entry” refers to an entry of a mapping data structure that is used to reference other entries within the forward map  160  (and/or other storage metadata  135 ). A reference entry may only exist while it is referenced by one or more other entries within the logical address space  132 . In some embodiments, reference entries may not be accessible to the storage clients  106  and/or may be immutable. The storage layer  130  may leverage reference entries to allow storage clients to reference the same set of data through multiple, different logical interfaces via a single reference entry interface. The contextual format of data on the storage medium  140  (data that is referenced by multiple LIDs) may be simplified to associate the data with the reference entries which, in turn, are associated with N other logical interface(s) through other persistent metadata (e.g., persistent notes  366 ). Relocating cloned data may, therefore, comprise updating a single mapping between the reference entry and the new storage address of the data segment. 
       FIG. 4A  is a block diagram of another embodiment of a system  400  for efficient open-to-close consistency. The system  400  includes a storage layer  130  that is configured to implement range clone operations by use of an intermediate mapping layer. The storage metadata  135  may comprise a forward map  160  pertaining to the logical address space  132 . The forward map  160  (and/or other storage metadata  135 ) may include information pertaining to allocations of the logical address space by the storage clients  106 , bindings between LIDs and storage addresses within the storage address space  144 , and so on, as disclosed above. 
     In the  FIG. 4A  embodiment, the logical interface management module  334  may comprise a reference module  434  configured to manage clone operations by use of a reference map  460 . The reference map  460  may comprise reference entries that correspond to data that is being referenced by one or more logical interfaces of the logical address space  132  (e.g., one or more sets of LIDs). The reference module  434  may be configured to remove reference entries that are no longer being used to reference valid data and/or are no longer being referenced by entries within the forward map  160 . As illustrated in  FIG. 4A , reference entries may be maintained separately from the forward map  160  (e.g., in a separate reference map  460 ). The reference entries may be identified by use of reference identifiers, which may be maintained in a separate namespace than the logical address space  132 . Accordingly, the reference entries may be part of an intermediate, “virtual” or “reference” address space  432  that is separate and distinct from the logical address space  132  that is directly accessible to the storage clients  106  through the storage layer interface  131 . Alternatively, in some embodiments, reference entries may be assigned LIDs selected from pre-determined ranges and/or portions of the logical address space  132  that are not directly accessible by the storage clients  106 . 
     The logical interface management module  334  may be configured to implement clone operations by linking one or more LID entries in the forward map  160  to reference entries in the reference map  460 . The reference entries may be bound to the storage address(es) of the cloned data. Accordingly, LIDs that are associated with cloned data may reference the underlying data indirectly through the reference map  460  (e.g., the LID(s) may map to reference entries which, in turn, map to storage addresses). Accordingly, entries in the forward map  160  corresponding to cloned data may be referred to as “indirect entries.” As used herein, an “indirect entry” refers to an entry in the forward map  160  that references and/or is linked to a reference entry in the reference map  460 . Indirect entries may be assigned a LID within the logical address space  132 , and may be accessible to the storage clients  106 . 
     As disclosed above, after cloning a particular set of LIDs, the storage clients  106  may perform storage operations within one or more of the cloned ranges, which may cause the clones to diverge from one another (in accordance with the clone mode). In a “copy-on-write” mode, changes made to a particular clone may not be reflected in the other cloned ranges. In the  FIG. 4A  embodiment, changes made to a clone may be reflected in “local” entries associated with an indirect entry. As used herein, a “local entry” refers to a portion of an indirect entry that is directly mapped to one or more storage addresses of the storage medium  140 . Accordingly, local entries may be configured to reference data that has been changed in a particular clone and/or differs from the contents of other clones. Local entries may, therefore, correspond to data that is unique to a particular clone. 
     The translation module  134  may be configured to access data associated with cloned data by use of, inter alia, the reference map  460  and/or reference module  434 . The translation module  134  may implement a cascade lookup, which may comprise traversing local entries first and, if the target front-identifier(s) are not found within local entries, continuing the traversal within the reference entries to which the indirect entry is linked. 
     The log storage module  136  and media management module  370  may be configured to manage the contextual format of cloned data. In the  FIG. 4A  embodiment, cloned data (data that is referenced by two or more LID ranges within the forward map  160 ) may be stored in a contextual format that associates the data with one or more reference entries of the reference map  460 . The persistent metadata stored with such cloned data segments may correspond to a single reference entry, as opposed to identifying each LID associated with the data segment. Creating a clone may, therefore, comprise updating the contextual format of the cloned data in one or more background operations by use of, inter alia, the media management module  370 , as disclosed above. 
       FIG. 4B  depicts one embodiment of a clone operation using a reference map  460 . In state  413 A, an entry corresponding to LID  10  extent  2  in the logical address space  132  (denoted  10 , 2  in  FIG. 4B ) may directly reference data at storage address  20000  on the storage medium  140 . Other entries are omitted from  FIG. 4B  to avoid obscuring the details of the disclosed embodiment. In state  413 B, the storage layer  130  implements an operation to clone the range  10 , 2 . Cloning the range  10 , 2  may comprise: a) allocating a new range of LIDs (denoted  400 , 2  in  FIG. 4B ) in the logical address space and b) allocating reference entries in the reference map  460  through which the entries  10 , 2  and  400 , 2  may reference the cloned data at storage address  20000  (denoted  100000 , 2  in  FIG. 4B ). The clone operation may further comprise associating the entries  10 , 2  and  400 , 2  with the reference entry  100000 , 2  as illustrated at state  413 C. As disclosed above, associating the entries  10 , 2  and  400 , 2  with the reference entry  100000 , 2  may comprise indicating that the entries  10 , 2  and  400 , 2  are indirect entries. State  413 C may further comprise storing a persistent note  366  on the storage medium  140  to associate the data at storage address  20000  with the reference entry  100000 , 2  and/or to associate the entries  10 , 2  and  400 , 2  with the reference entry  100000 , 2  in the reference map  460 . 
     The storage layer  130  may provide access to the data segment at storage address  20000  through either LID  10  or  400  (through the reference entry  100000 , 2 ). In response to a request pertaining to LID  10  or  400 , the translation module  134  may determine that the corresponding entry in the forward map  160  is an indirect entry that is associated with an entry in the reference map  460 . In response, the reference module  434  performs a cascade to determine the storage address by use of local entries within the forward map  160  (if any) and the corresponding reference entries in the reference map  460  (e.g., reference entry  100000 , 2 ). 
     Creating the clone at step  413 C may comprise modifying the logical interface of the data segment stored at step  20000  to associate the data with both LID ranges  10 , 2  and  400 , 2 . The contextual format of the data, however, may only associate the data with LIDs  10 , 2 . As disclosed above, creating the clone may further comprise storing a persistent note  366  on the storage medium  140  to associate the data segment with the LIDs  10 , 2  and  400 , 2  through the reference entry  100000 , 2 . The data segment may be rewritten in an updated contextual format in one or more background operations performed by the media management module  370 . The data may be stored with persistent metadata  314  that associates the data segment with the reference entry  100000 , 2  as opposed to the separate LID ranges  10 , 2  and  400 , 2 . Therefore, relocating the data segment (as shown in state  413 D) may only require updating a single entry in the reference map  460  as opposed to multiple entries corresponding to each LID range that references the data (e.g., multiple entries  10 , 2  and  400 , 2 ). Moreover, any number of LID ranges in the forward map  160  may reference the data segment, without increasing the size of the persistent metadata  314  associated with the data on the storage medium  140  and/or complicating the operation of the media management module  370 . 
       FIG. 4C  depicts another embodiment of a clone operation implemented using reference entries. In response to a request to create a clone of the LIDs  1024 - 2048  and/or data segment  312 , the logical interface management module  334  may be configured to allocate a reference entry  482  in the reference map  460  to represent the data segment  312 . Any number of LID (s) in the forward map  160  may reference the data through the reference entry  482 , without increasing the overhead of the persistent metadata associated with the data segment  312  and/or complicating the operation of the media management module  370 . As depicted in  FIG. 4C , the reference entry  482  may be bound to the storage addresses of the data segment  312  (storage addresses  64432 - 65456 ). The entries  462  and  472  in the forward map  160  may reference the storage addresses indirectly, through the reference entry  482  (e.g., may be linked to the reference entry  482  as illustrated in  FIG. 4C ). 
     In the  FIG. 4C  embodiment, the reference entry  482  is assigned identifiers  0 Z- 1024 Z. The identifier (s) of the reference entry  482  may correspond to a particular portion of the logical address space  132  or may correspond to a different, separate namespace. The storage layer  130  may link the entries  462  and  472  to the reference entry  482  by use of, inter alia, metadata associated with the entries  462  and/or  472 . Alternatively, or in addition, the indirect entries  462  and/or  472  may replace storage address metadata with references and/or links to the reference entry  482 . The reference entry  482  may not be directly accessible by storage clients  106  via the storage layer  130 . 
     The clone operation may further comprise modifying the logical interface  311 D of the data segment  312 ; the modified logical interface  311 D may allow the data segment  312  to be referenced through the LIDs  1024 - 2048  of the indirect entry  462  and/or  6144 - 7168  of the indirect entry  472 . Although the reference entry  482  may not be accessible to the storage clients  106 , the reference entry  482  may be used to access the data by the translation module  134  (through the indirect entries  462  and  472 ), and as such, may be considered to be part of the modified logical interface  311 B of the data segment  312 . 
     The clone operation may further comprise storing a persistent note  366 A on the storage medium  140 . As disclosed above, storage of the persistent note(s)  366 A and/or  366 B may ensure that the clone operation is persistent and crash safe. The persistent note  366 A may be configured to identify the reference entry  482  associated with the data segment  312 . Accordingly, the persistent note  366 A may associate the storage addresses  64432 - 65456  with the reference entry identifier(s)  0 Z- 1024 Z. The clone operation may further comprise storing another persistent note  366 B configured to associate the LIDs of the entries  462  and/or  472  with the reference entry  482 . Alternatively, metadata pertaining to the association between entries  462 ,  472 , and  482  may be included in a single persistent note. The persistent notes  366 A and/or  366 B may be retained on the storage medium  140  until the data segment  312  is relocated in an updated contextual format and/or the forward map  160  (and/or reference map  460 ) is persisted. 
     The modified logical interface  311 D of the data segment  312  may be inconsistent with the contextual format original data packet  410 A; the persistent metadata  314 A may reference LIDs  1024 - 2048  rather than the reference entry  482  and/or the cloned entry  472 . The storage layer  130  may be configured to store the data segment  312  in an updated contextual format (packet  410 B) that is consistent with the modified logical interface  311 D; the persistent metadata  314 B may associate the data segment  312  with the reference entry  482 , as opposed to separately identifying the LID(s) within each cloned range (e.g., entries  462  and  472 ). Accordingly, the use of the indirect entry  482  allows the logical interface  311 D of the data segment  312  to comprise any number of LIDs, independent of size limitations of the persistent metadata  314 A-B. Moreover, additional clones of the reference entry  482  may be made without updating the contextual format of the data segment  312 ; such updates may be made by associating the new LID ranges with the reference entry  482  in the forward map  160  and/or by use of, inter alia, persistent notes  366 . 
     As disclosed above, the indirect entries  462  and/or  472  may initially reference the data segment  312  through the reference entry  482 . Storage operations performed subsequent to the clone operation may be reflected by use of local entries within the forward map  160 . After completion of the clone operation, the storage layer  130  may modify data associated with one or more of the cloned LID(s). In the  FIG. 4D  embodiment, a storage client  106  modifies and/or overwrites data corresponding to LIDs  1024 - 1052  of the indirect entry  462 , which may comprise appending a new data segment  412  to the storage log (in data packet  420  at storage addresses  7823 - 7851 ). 
     The data segment  412  may be stored in a contextual format (data packet  420 ) comprising persistent metadata  414 A configured to associate the data segment  412  with LIDs  1024 - 1052 . The storage layer  130  may be configured to associate the data segment  412  with the LIDs  1024 - 1052  in a local entry  465 . The local entry  465  may reference the updated data directly, as opposed to referencing the data through the indirect entry  462  and/or reference entry  482 . 
     In response to a request pertaining to data  1024 - 1052  (or subset thereof), the logical interface management module  334  may search for references to the requested LIDs in a cascade lookup operation, which may comprise searching for references to local entries (if available) followed by the reference entries. In the  FIG. 4D  embodiment, the local entry  465  may be used to satisfy requests pertaining to the LID range  1024 - 1052  (storage addresses  7823 - 7851 ) rather than  64432 - 64460  per the reference entry  462 . Requests for LIDs that are not found in a local entry (e.g., LIDs  1053 - 2048 ) may continue to be serviced through the reference entry  482 . The logical interface  311 E of the data pertaining to the range  1024 - 2048  may, therefore, comprise one or more local entries  465 , one or more indirect entries  462 , and/or one or more reference entries  482 . 
     In a further embodiment, illustrated in  FIG. 4E , a storage layer  130  may modify data of the clone through another one of the LIDs of the logical interface  311 E (e.g., LIDs  6144 - 6162 ); the logical interface delimiters are not shown in  FIG. 4E  to avoid obscuring the details of the illustrated embodiment. The modified data may be referenced using a local entry  475 , as disclosed above. In the  FIG. 4E  embodiment, each of the ranges  462  and  472  has its own, respective local version of the data formerly referenced through identifiers  0 Z- 52 Z of the reference entry  482 . As such, neither entry  462  nor  472  includes a reference to the range  0 Z- 52 Z. The reference module  434  may determine that the corresponding data (and reference identifiers) is no longer being referenced, and as such, may be marked for removal from the storage medium  140  (e.g., invalidated). As depicted in  FIG. 4E , invalidating the data may comprise removing references to the data from the reference map  460  by, inter alia, modifying the reference entry  482  to remove the range  0 Z- 52 Z. Invalidating the data may further comprise updating other storage metadata  135 , such as a reverse map, validity bitmaps, and/or the like (e.g., to indicate that the data stored at storage addresses  64432 - 64484  does not need to be retained). The ranges of entries  462  and  472  may continue to diverge, until neither references any portion of the reference entry  482 , at which point the reference entry  482  may be removed and the data referenced thereby may be invalidated, as disclosed above. 
     Although  FIGS. 4D and 4E  depict local entries  465  and  475  that comprise overlapping LID ranges with the corresponding indirect entries  462  and  472 , the disclosure is not limited in this regard. In some embodiments, the storage operation of  FIG. 4D  may be reflected by creating the local entry  465  and modifying the indirect entry  462  to reference only the LIDs  1053 - 2048 . Similarly, the operation of  FIG. 4E  may comprise creating the local entry  475  and modifying the indirect entry  472  to reference a truncated LID range  6163 - 7168 . 
     Referring back to  FIG. 4A , the reference module  434  may be configured to manage or “groom” the reference map  460 . In some embodiments, each entry in the reference map  460  comprises metadata that includes a reference count. The reference count may be incremented as new references or links to the reference entry are added, and may be decremented in response to removing references to the entry. In some embodiments, reference counts may be maintained for each reference identifier in the reference map  460 . Alternatively, reference counts may be maintained for reference entries as a whole. When the reference count of a reference entry reaches 0, the reference entry (and/or a portion thereof) may be removed from the reference map  460 . Removing a reference entry (or portion of a reference entry) may comprise invalidating the corresponding data on the storage medium  140 , as disclosed herein (indicating that the data no longer needs to be retained). 
     In another embodiment, the reference module  434  may remove reference entries using a “mark-and-sweep” approach. The reference module  434  (or other process, such as the translation module  134 ) may periodically check references to entries in the reference map  460  by, inter alia, following links to the reference entries from indirect entries (or other types of entries) in the forward map  160 . Reference entries that are not accessed during the mark-and-sweep may be removed, as disclosed above. The mark-and-sweep may operate as a background process, and may periodically perform a mark-and-sweep operation to identify and remove reference entries that are no longer in use. 
     In some embodiments, the reference map  460  disclosed herein may be created on demand (e.g., in response to creation of a clone, or other indirect data reference). In other embodiments, all data storage operations may be performed through intermediate mappings. In such embodiments, storage clients  106  may allocate indirect, virtual identifiers (VIDs) of a virtual address space (VAS), which may be linked to and/or reference storage addresses through an intermediate mapping layer, such as the logical address space  132 . The VAS may add an intermediate mapping layer between storage clients  106  and the storage medium  140 . Storage clients  106  may reference data using VIDs of a virtualized address space that map to logical identifiers of the logical address space  132 , and which, in turn, are associated with storage addresses on respective storage device(s)  141  and/or storage medium  140 . As used herein, a VAS may include, but is not limited to, a Logical Unit Number (LUN) address space, a virtual LUN (vLUN) address space, and/or the like. 
       FIG. 5A  depicts one embodiment of an aggregation layer  530  configured to implement, inter alia, efficient range clone operations using a virtualized address space  532 . The aggregation layer  530  may be configured to present a VAS  532  to the storage clients  106  through an interface  531 . Like the interface  131  disclosed herein, the interface  531  may comprise one or more of a block device interface, virtual storage interface, cache interface, and/or the like. Storage clients  106  may perform storage operations pertaining to storage resources managed by the aggregation layer  530  by reference to VIDs of the VAS  532  through the interface  531 . 
     The aggregation layer  530  may further comprise a VAS translation module  534  configured to map VIDs to storage resources through one or more intermediary storage layers (e.g., storage layer  130 ). Accordingly, the VAS metadata  535  of the aggregation layer  530  may include a VAS forward map  560  comprising any-to-any mappings between VIDs of the VAS  532  and LIDs of the VAS  532 . Although not depicted in  FIG. 5A , the VAS translation module  534  and/or VAS forward map  560  may be configured to aggregate a plurality of logical address spaces  132  of a plurality of different storage layers  130  into a single VAS  532 . Accordingly, in some embodiments, a VAS  532  may correspond to a plurality of different logical address spaces  132 , each comprising a separate set of LIDs, and each corresponding to a respective storage layer  130 , storage device  141 , and/or storage medium  140 . 
     Although  FIG. 5A  depicts the aggregation layer  530  separately from the storage layer  130 , the disclosure is not limited in this regard. In some embodiments, VAS  532 , VAS forward map  560 , VAS translation module  534 , and/or other modules of the aggregation layer  530  may be implemented as part of the storage layer  130 . 
     The aggregation layer  530  may be configured to leverage the intermediary virtual address space provided by the VAS  532  to, inter alia, implement efficient range clone, move, merge, and/or other high-level operations. Alternatively, or in addition, the intermediary mapping layer(s) may be leveraged to enable efficient clone operations on random access, write-in-place storage devices, such as hard disks and/or the like. 
     Storage clients  106  may perform storage operations in reference to VIDs of the VAS  532 . Accordingly, storage operations may comprise two (or more) translation layers. The VAS forward map  560  may comprise a first translation layer between VIDs of the VAS  532  and identifiers of the logical address space  132  of the storage layer  130 . The forward map  160  of the storage layer  130  may implement a second translation layer between LIDs and storage address(es) on the storage medium  140 . 
     The aggregation layer  530  may be configured to manage allocations within the VAS  532  by use of, inter alia, the VAS metadata  535 , VAS forward map  560 , and/or VAS translation module  534 . In some embodiments, allocating a VID in the VAS  532  may comprise allocating one or more corresponding LIDs in the logical address space  132  (and/or identifiers of one or more other storage layers). Accordingly, each VID allocated in the VAS  532  may correspond to one or more LIDs of the logical address space  132 . The any-to-any mappings between the VIDs of the aggregation layer  530  and the logical address space  132  may be sparse and/or any-to-any, as disclosed herein. Moreover, in some embodiments, the aggregation layer  530  may be configured to maintain any-to-any and/or range managed mappings between VIDs and a plurality of different logical address spaces  132 . Accordingly, the aggregation layer  530  may aggregate and/or combine the logical address spaces of a plurality of different storage devices  141  managed by different respective storage layers  130  into a single, aggregate VAS  532 . 
     In the  FIG. 5A  embodiment, the logical address space  132  may not be directly accessible, and as such, storage clients  106  may reference storage resources using VIDs through the interface  531 . Therefore, performing a storage operation through the aggregation layer  530  in reference to one or more VIDs may comprise: a) identifying the storage layer  130  corresponding to the VIDs, b) determining the LID(s) of the storage layer  130  that are mapped to the VIDs by use of the VAS translation module  534  and/or VAS forward map  560 ; and c) implementing the storage operation by use of the storage layer  130  in reference to the determined LID (s). 
       FIG. 5B  depicts one embodiment of a clone operation implemented by use of the aggregation layer  530 . As disclosed above, the VAS forward map  560  may correspond to a VAS  532  that is indirectly mapped to storage addresses through a logical address space  132  of a storage layer  130 .  FIG. 5B  illustrates the addressing layers used to implement storage operations through the aggregation layer  530 . The VIDs of the VAS  532  may comprise the top-level addressing layer that is accessible to storage clients  106  through, inter alia, the interface  531  of the aggregation layer  530 . The logical address space  132  of the storage layer  130  may comprise an intermediary addressing layer. The VAS forward map  560  may comprise any-to-any mappings between VIDs and LIDs. The LIDs may be mapped to storage addresses within the storage address space  144  by use of the forward map  160 . Accordingly, VIDs may be mapped to the storage address space  144  through the intermediate logical address space of the storage layer  130 . 
     As illustrated in  FIG. 5B , in state  563 A, the VAS forward map  560  may comprise an entry  10 , 2  that represents two VIDs ( 10  and  11 ) in the VAS  532 . The VAS forward map  560  associates the VID entry  10 , 2  with LIDs of the logical address space  132 . In the  FIG. 5B  embodiment, the VAS forward map  560  binds the VID entry  10 , 2  to LIDs  100000  and  100001  (entry  100000 , 2 ). The entry  10 , 2  may be allocated to a particular storage client  106 , which may perform storage operations in reference to the VIDs. In state  563 A, the storage layer  130  may be configured to map the entry  100000 , 2  to one or more storage addresses on the storage medium  140  (storage address  20000 ). 
     In state  536 B, the aggregation layer  530  may implement a clone operation to clone the VID entry  10 , 2 . The clone operation may comprise: a) allocating a new VID entry  400 , 2  and b) associating the new VID entry  400 , 2  with the corresponding entry  100000 , 2  in the VAS forward map  560 . The corresponding entry  100000 , 2  in the forward map  160  may remain unchanged. Alternatively, a reference count (or other indicator) of the entry  100000 , 2  in the forward map  160  may be updated to indicate that the entry is being referenced by multiple VID ranges. The contextual format of the data stored at storage address  20000  may be left unchanged (e.g., continue to associate the data with the logical interface  100000 , 2 ). The clone operation may further comprise storing a persistent note  366  on the storage medium  140  to indicate the association between the VID entry  400 , 2  and the entry  100000 , 2  in the forward map  160 . Alternatively, or in addition, the clone operation may be made persistent and/or crash safe by persisting the VAS forward map  560  (and/or portions thereof). 
     In state  536 C, the data at storage address  20000  may be relocated to storage address  40000 . The relocation may occur in a standard storage media maintenance operation, and not to update the contextual format of the cloned data. Relocating the data may comprise updating a single entry in the forward map  160 . The VAS forward map  560  may remain unchanged. Modifications to the different versions of the VID ranges  10 , 2  and  400 , 2  may be managed through the intermediary, logical address space. A modification to VID  10  may comprise: a) allocating a new LID in the logical address space  132 , b) storing the modified data in association with the new LID, and c) mapping the new LID to VID  10  in the VAS forward map  560 . 
     The embodiments for implementing range clone, move, and/or merge operations disclosed herein may be used to efficiently implement other, higher-level storage operations, such as snapshots, deduplication, atomic operations, transactions, file-system management functionality, and/or the like. Referring back to  FIG. 4A , the storage layer  130  may comprise a deduplication module  374  configured to identify duplicate data on the storage medium  140 . Duplicate data may be identified using any suitable mechanism. In some embodiments, duplicate data is identified by: a) scanning the contents of the storage medium  140 , b) generating signature values for various data segments, and c) comparing data signature values to identify duplicate data. The signature values may include, but are not limited to, cryptographic signatures, hash codes, cyclic codes, and/or the like. Signature information may be stored within storage metadata  135 , such as the forward map  160  (e.g., in metadata associated with the entries), and/or may be maintained and/or indexed in one or more separate datastructures of the storage metadata  135 . The deduplication module  374  may compare data signatures and, upon detecting a signature match, may perform one or more deduplication operations. The deduplication operations may comprise verifying the signature match (e.g., performing a byte-by-byte data comparison) and performing one or more range clone operations to reference the duplicate data through two or more LID ranges. 
       FIG. 6  depicts one embodiment of a deduplication operation. The forward map  160  may comprise entries  662  and  672 , which may reference duplicated data stored at different respective storage addresses  3453 - 4477  and  7024 - 8048 . The entries  662  and  672  may correspond to different, respective logical interfaces  663  and  673  corresponding to LIDs  1024 - 2048  and  6144 - 6656 , respectively. The duplicated data segment (data segment  612 ) may be identified and/or verified by the deduplication module  374 , as disclosed above. Alternatively, the duplicated data may be identified as data is received for storage at the storage layer  130 . Accordingly, the data may be deduplicated before an additional copy of the data is stored on the storage medium  140 . 
     In response to identifying and/or verifying that the entries  662  and  672  reference duplicate data, the storage layer  130  may be configured to deduplicate the data, which may comprise creating one or more range clones to reference a single copy of the duplicate data through two different sets of LIDs. As disclosed above, creating a range clone may comprise modifying the logical interface(s)  663  and  673  of a data segment. In the  FIG. 6  embodiment, the duplicated data is stored as a data segment  612  within a packet  610  at storage locations  3453 - 4477  and  7024 - 8048 , respectively. The clone operation may comprise modifying the logical interface of one of the data segments (or a new version and/or copy of the data segment), such that the data segment can be referenced by both entries  663  and  673 . 
     The range clone operation may be implemented using any of the clone embodiments disclosed herein including the range clone embodiments of  FIGS. 3A-E , the reference entry embodiments of  FIGS. 4A-E , and/or the intermediate mapping embodiments of  FIGS. 5A-B . In the de-deduplication embodiment of  FIG. 6 , both LID ranges  1024 - 2048  and  6144 - 7168  may be modified to reference a single version of the data segment  612  (the other data segment may be invalidated) through a reference entry  682 . As such, the deduplication operation may comprise creating a reference entry  682  to represent the deduplicated data segment  612  (reference the packet  610 ). The deduplication operation may further comprise modifying and/or converting the entries  662  and  672  into respective indirect entries  665  and  675 , which may be mapped to the data segment  612  through the reference entry  682 , as disclosed above. The deduplication operations may further comprise modifying the logical interface  669  of the data segment  612  to associate the data segment  612  with both sets of LIDs  1024 - 2048  and  6144 - 7168  (as well as the reference entry  682 ). The deduplication operations may further comprise storing a persistent note  366  on the storage medium  140 , as disclosed above. 
     The deduplication operation may further comprise updating the contextual format of the data segment  612  to be consistent with the modified logical interface  669 , as disclosed above. Updating the contextual format may comprise appending the data segment  612  in an updated contextual format (data packet  610 ) to the storage log (e.g., at storage locations  84432 - 85456 ) in one or more background operations. The updated data packet  610  may comprise persistent metadata  614  that associates the data segment  612  with the updated logical interface  669  (e.g., LIDs  1024 - 2048  and  6144 - 6656  through reference identifiers  0 Z- 1023 Z). 
     Although  FIG. 6  illustrates cloning and/or deduplicating a single entry or range of LIDs, the disclosure is not limited in this regard. In some embodiments, a plurality of front-identifier ranges may be cloned in a single clone operation. This type of clone operation may be used to create a “snapshot” of an address range (or entire logical address space  132 ). As used herein, a snapshot refers to the state of a storage device (or set of LIDs) at a particular point in time. The snapshot may maintain an “original” state of a LID range regardless of changes that occur within the range after completing the snapshot operation. 
       FIG. 7  is a block diagram depicting one embodiment of a system  700  comprising a storage layer  130  configured to efficiently implement snapshot operations. The  FIG. 7  embodiment pertains to an address range within a logical address space  132 . The disclosure is not limited in this regard, however, and could be adapted for use with other types of address ranges, such as ranges and/or extents within a VAS  532 , as disclosed above. The storage layer  130  may comprise a snapshot module  736  and timing module  738  configured to implement snapshot operations as disclosed herein. 
     In state  773 A, the storage layer  130  may be configured to create a snapshot of a LID range FR1. Creating the snapshot may comprise preserving the state of the LID range FR1 at a particular time. The snapshot operation may further comprise preserving the LID range FR1 while allowing subsequent storage operations to be performed within the LID range. 
     As disclosed above, the storage layer  130  may be configured to store data in a storage log on the storage medium  140  by use of, inter alia, the log storage module  136 . The log order of storage operations may be determined using sequence information associated with data packets, such as sequence indicators  113  on storage divisions  170 A-N and/or sequential storage locations within the storage address space  144  of the storage medium  144  (as disclosed in conjunction with  FIGS. 1D and 1E ). 
     The storage layer  130  may be further configured to maintain other types of ordering and/or timing information, such as the relative time ordering of data in the log. However, in some embodiments, the log order of data may not accurately reflect timing information due to, inter alia, data being relocated within the storage device in media management operations. Relocating data may comprise reading the data from its original storage location on the storage medium  140  and appending the data at a current append point within the storage log. As such, older, relocated data may be stored with newer, current data in the storage log. Therefore, although the storage log may preserve the relative log order of data operations pertaining to particular LIDs, the storage log may not accurately reflect absolute timing information. 
     In some embodiments, the log storage module  136  is configured to associate data with timing information, which may be used to establish relative timing information of the storage operations performed on the storage medium  130 . In some embodiments, the timing information may comprise respective timestamps (maintained by the timing module  738 ), which may be applied to each data packet stored on the storage medium  140 . The timestamps may be stored within persistent metadata  314  of the data packets  310 . Alternatively, or in addition, the timing module  738  may be configured to track timing information at a coarser level of granularity. In some embodiments, the timing module  738  maintains one or more global timing indicators (an epoch identifier). As used herein, an “epoch identifier” refers to an identifier used to determine relative timing of storage operations performed through the storage layer  130 . The log storage module  136  may be configured to include an epoch indicator  739  in data packets  710 . The epoch indicator  739  may correspond to the current epoch (e.g., global timing indicator) maintained by the timing module  738 . The epoch indicator  739  may correspond to the epoch in which the corresponding data segment  712  was written to the storage log. The epoch indicator  739  may be stored within the persistent metadata  714  of the packet  710 , and as such, may remain associated with the data packet  710  during relocation operations. The timing module  738  may be configured to increment the global epoch identifier in response to certain events, such as the creation of a new snapshot, a user request, and/or the like. The epoch indicator  739  of the data segment  712  may remain unchanged through relocation and/or other media maintenance operations. Accordingly, the epoch indicator  739  may correspond to the original storage time of the data segment  712  independent of the relative position of the data packet  710  in the storage log. 
     A snapshot operation may comprise preserving the state of a particular LID range (FR1) at a particular time. A snapshot operation may, therefore, comprise preserving data pertaining to FR1 on the storage medium  140 . Preserving the data may comprise: a) identifying data pertaining to a particular timeframe (epoch) and b) preserving the identified data on the storage medium  140  (e.g., preventing the identified data being removed from the storage medium  140  in, inter alia, storage recovery operations). Data pertaining to a snapshot may be retained despite being invalidated by subsequent storage operations (e.g., operations that overwrite, modify, TRIM, and/or otherwise obviate the data). Data that needs to be preserved for a particular snapshot may be identified by use of the epoch indicators  739  disclosed above. 
     In state  773 A (time t1, denoted by epoch indicator e0), the storage layer  130  may receive a request to implement a snapshot operation. In response to the request, the snapshot module  736  may determine the current value of the epoch identifier maintained by the timing module  738 . The current value of the epoch identifier may be referred to as the current “snapshot epoch.” In the  FIG. 7  embodiment, the snapshot epoch is 0. The snapshot module  736  may be further configured to cause the timing module  738  to increment the current, global epoch indicator (e.g., increment the epoch identifier to 1). Creating the snapshot may further comprise storing a persistent note  366  on the storage medium configured to indicate the current, updated epoch indicator. The persistent note  366  may be further configured to indicate that data pertaining to the snapshot epoch is to be preserved (e.g., identify the particular range of LIDs FR1 to be preserved in the snapshot operation). The persistent note  366  may be used during metadata reconstruction operations to: a) determine the current epoch identifier and/or b) configure the snapshot module  736  and/or media management module  370  to preserve data associated with a particular snapshot epoch (e.g., epoch e0). 
     The snapshot module  736  may be further configured to instruct the media management module  370  to preserve data associated with the snapshot epoch. In response, the media management module  370  may be configured to: a) identify data to preserve for the snapshot (snapshot data), and b) prevent the identified data from being removed from the storage medium  140  in, inter alia, storage recovery operations. The media management module  370  may identify snapshot data by use of the epoch indicators  739  of the data packets  710 . As disclosed in conjunction with  FIG. 1E , data may be written out-of-place on the storage medium  140 . The most current version of data associated with a particular LID may be determined based on the order of the corresponding data packets  710  within the log. The media management module  370  may be configured to identify the most current version of data within the snapshot epoch as data that needs to be preserved. Data that has been rendered obsolete by other data in the snapshot epoch may be removed. Referring to the  FIG. 1E  embodiment, if the data X0 and X1 (associated with the same LID A) were both marked with the snapshot epoch 0, the media management module  370  would identify the most current version of the data in epoch 0 as X1, and would mark the data X0 for removal. If, however, data X0 were marked with snapshot epoch 0 and X1 where marked with a later epoch (e.g., epoch 1, after the snapshot operation), the media management module  370  may preserve the data X0 on the storage medium  140  in order to preserve the data of the snapshot. 
     In state  773 B, the snapshot module  738  may be configured to preserve data pertaining to the snapshot FR1 (data associated with epoch e0), while allowing storage operations to continue to be performed during subsequent epochs (e.g., epoch e1). Preserving FR1 may comprise cloning FR1 to preserve the original status of the LID range at epoch e0 (FR1 (e0)), while allowing storage operations to continue with reference to FR1. The clone operation may be implemented as disclosed above using one or more of duplicated entries, reference entries, and/or an intermediate mapping layer. The storage operations may comprise appending data to the storage log on the storage medium  140  in reference to the LIDs FR1. The cloned LIDs corresponding to the snapshot FR1 (e0) may be immutable. Accordingly, the snapshot of FR1 (e0) may be preserved despite changes to the LID range. Data stored in state  773 B may be stored with an epoch indicator  739  of the current epoch (e1). The snapshot module  736  may be configured to preserve data that is rendered obsolete and/or invalidated by storage operations performed during epoch e1 (and subsequent epochs). Referring back to the  FIG. 1E  embodiment, the media management module  370  may identify data X0 as data to preserve for the snapshot FR1 (the data X1 may have been stored after the snapshot operation was performed). The snapshot module  738  and/or media management module  370  may be configured to preserve the data X0 even through the data was subsequently made obsolete by data X1 in epoch e1. The data X0 may be retained even if the LID A is deleted, TRIMed, or the like. 
     The snapshot of FR1 (e0), including the LID range FR1 (e0) and the data marked with epoch indicator e0, may be preserved until the corresponding snapshot is deleted. The snapshot may be deleted in response to a request received through the interface  131 . As indicated in state  773 C, the epoch 0 may be retained on the storage medium  140  even after other, intervening epochs (epochs e1-eN) have been created and/or deleted. Deleting the epoch e0 may comprise configuring the snapshot module  738  and/or media management module  370  to remove invalid/obsolete data associated with the epoch e0. 
     Storage operations performed after creating the snapshot at state  773 A may modify the logical address space  132  and specifically the forward map  160 . The modifications may comprise updating storage address bindings in response to appending data to the storage medium  140 , adding and/or removing LIDs to FR1, and so on. In some embodiments, the snapshot module  736  is configured to preserve the snapshot range FR1 (e0) within separate storage metadata  135 , such as a separate region of the logical address space  132 , in a separate namespace, in a separate map, and/or the like. Alternatively, the snapshot module  736  may allow the changes to take place in the forward map  160  without preserving the original version of FR1 at time e0. The snapshot module  736  may be configured to reconstruct the forward map  160  for e0 (time t1) using the snapshot data preserved on the storage medium  140 . The forward map  160  at time t1 may be reconstructed, as disclosed above, which may comprise sequentially accessing data stored on the storage medium  140  (in a log-order) and creating forward map entries based on persistent metadata  714  associated with the data packets  710 . In the  FIG. 7  embodiment, forward map  160  corresponding to epoch e0 may be reconstructed by referencing data packets  710  that are marked with the epoch indicator  739  e0 (or lower). Data associated with epoch indicators  739  greater than e0 may be ignored (since such data corresponds to operations after creation of the snapshot FR1 (e0) was created). 
     The storage layer  130  disclosed herein may be further configured to implement efficient range move operations.  FIG. 8A  depicts one embodiment of a move operation implemented by the storage layer  130  disclosed herein. The forward map  160  includes entries  862  configured to bind LIDs  1023 - 1025  to respective data segments on the storage medium  140 . The entries  862  are depicted separately to better illustrate details of the embodiment; however, the entries  862  could be included in a single entry comprising the full range of LIDs  1023 - 1025 . The entries  862  may define a logical interface  863  of the data stored at storage addresses  32 ,  3096 , and  872 . As disclosed above, the data stored at storage addresses  32 ,  3096 , and  872  may be stored in a contextual format that associates the data with the corresponding LID (s)  1023 ,  1024 , and  1025 . 
     The storage layer  130  may be configured to move the entries  862  to LIDs  9215 - 9217  by, inter alia, replacing the association between the LIDs  1023 ,  1024 , and  1025  and the data at the respective media storage locations  32 ,  3096 , and  872  with a new logical interface  863 B corresponding to the new set of LIDs (e.g.,  9215 ,  9216 , and  9217 ). The move operation may be performed in response to a request received via the interface  131  and/or as part of a higher-level storage operation (e.g., a request to rename a file, operations to balance and/or defragment the forward map  160 , or the like). 
     The move operation may be implemented in accordance with one or more of the cloning embodiments disclosed above. In some embodiments, the move operation may comprise associating the storage addresses mapped to LIDs  1023 ,  1024 , and  1025  with the destination LIDs  9215 ,  9216 , and  9217 , which may result in modifying the logical interface  863 A of the data in accordance with the move operation. The move operation may further comprise storing a persistent note  366  on the storage medium  140  to ensure that the move operation is persistent and crash safe. The data stored at storage addresses  32 ,  872 , and  3096  may be rewritten in accordance with the updated logical interface  863 B in one or more background operations, as disclosed above. 
       FIG. 8B  depicts another embodiment of a move operation. As above, the move operation may comprise moving the data associated with LIDs  1023 - 1025  to LIDs  9215 - 9217 . The move operation of  FIG. 8B  may utilize the reference entries as disclosed in conjunction with  FIGS. 4A-E . Accordingly, the move operation may comprise creating reference entries  882  in a reference map  460  to represent the move operation. The move operation may further comprise allocating new indirect entries  866  to reference the data through the reference entries  882 . Reference entries  882  may comprise the pre-move LIDs  1023 ,  1024 , and  1025 , which may be associated with the addresses  32 ,  3096 , and  872 . The new logical interface  863 C of the data may, therefore, comprise the indirect entries  866  and the corresponding reference entries  882 . The move operation may further comprise storing a persistent note  366  on the storage medium to ensure that the move operation is persistent and crash safe, as disclosed above. 
     The contextual format of the data stored at storage addresses  32 ,  3096 , and  872  may be inconsistent with the updated logical interface  863 C; the contextual format of the data may associate the respective data segments with LIDs  1023 ,  1024 , and  1025  as opposed to  9215 ,  9216 , and  9217  (and/or the reference entries). The persistent note  366  may comprise the updated logical interface  863 C of the data, so that the storage metadata  135  (e.g., forward map  160  and/or reference map  460 ) can be correctly reconstructed if necessary. 
     The storage layer  130  may provide access to the data in the inconsistent contextual format through the modified logical interface  863 C (LIDs  9215 ,  9216 , and  9217 ). The data may be rewritten and/or relocated in a contextual format that is consistent with the modified logical interface  863 C subsequent to the move operation (outside of the path of the move operation and/or other storage operations). In some embodiments, the data at storage addresses  32 ,  3096 , and/or  872  may be rewritten by a media management module  370  in one or more background operations, as described above. Therefore, the move operation may complete (and/or return an acknowledgement) in response to updating the forward map  160  and/or storing the persistent note  366 . 
     As illustrated in  FIG. 8C , the forward map  160  and/or other storage metadata  135  may be updated in response to rewriting data of the move operation. In the  FIG. 8C  embodiment, the data segment  812 A stored at media storage location  32  may be relocated in a storage recovery operation, which may comprise storing the data in a contextual format (data packet  810 A) that is consistent with the modified logical interface  863 C. The data packet  810 A may comprise persistent metadata  814 A that associates the data segment  812 A with LID  9215 . The forward map  160  may be updated to reference the data in the updated contextual format, which may comprise modifying the indirect entry of the LID  9215  to directly reference the data packet  810 A rather than the reference entry. The entry corresponding to LID  9215  may revert from an indirect entry to a standard, local entry, and the reference entry for LID  1023  may be removed from the reference map  460 . 
     Referring to  FIG. 8D , a storage client  106  may modify data associated with LID  9217 , which may comprise storing a data segment out-of-place (e.g., at storage address  772 ). The data segment may be written in a contextual format that is consistent with the modified logical interface  863 C (e.g., associates the data with LID  9217 ). In response, the forward map  160  may be updated to associate the entry for LID  9217  with the storage address of the data segment (e.g., storage address  772 ) and to remove the reference entry for LID  1025  from the reference map  460 , as disclosed above. 
     In some embodiments, the reference map  460  may be maintained separately from the forward map  160 , such that the entries therein (e.g., entries  882 ) cannot be directly referenced by storage clients  106 . This segregation may allow storage clients  106  to operate more efficiently. For example, rather than stalling operations until data is rewritten and/or relocated in the updated contextual format, data operations may proceed while the data is rewritten in one or more background processes. Referring to  FIG. 8E , following the move operation disclosed above, a storage client  106  may store data in connection with the LID  1024 . The reference entry  882  corresponding to the LID  1024  may be included in the reference map  460 , due to, inter alia, the data at storage address  3096  not yet being rewritten in the updated contextual format. However, since the reference map  460  is maintained separately from the forward map  160 , a name collision may not occur and the storage operation may complete. The forward map  160  may include a separate entry  864  comprising the logical interface for the data stored at media storage location  4322 , while continuing to provide access to the data formerly bound to LID  1024  through the logical interface  863 C (and reference map  460 ). 
     In the disclosed move operation, when the indirect entries are no longer linked to reference entries of the reference map  460  due to, inter alia, rewriting, relocating, modifying, deleting, and/or overwriting the corresponding data, the reference entries may be removed, and the indirect entries may revert to direct, local entries. In addition, the persistent note  366  associated with the move operation may be invalidated and/or removed from the storage medium  140 , as disclosed above. 
     Referring back to  FIG. 1A , the interface  131  of the storage layer  130  may be configured to provide APIs and/or interfaces for performing the storage operations disclosed herein. The APIs and/or interfaces may be exposed through one or more of the block interface, an extended storage interface, and/or the like. The block interface may be extended to include additional APIs and/or functionality by use of interface extensions, such as fadvise parameters, I/O control parameters, and the like. The interface  131  may provide APIs to perform range clone operations, range move operations, range merge operations, deduplication, snapshot, and other, higher-level operations disclosed herein. The interface  131  may allow storage clients  106  to apply attributes and/or metadata to LID ranges (e.g., freeze a range), manage range snapshots, and so on. As disclosed herein, a range clone operation comprises creating a logical copy of a set of one or more source LIDs. Range clone, move, and/or merge operations may be implemented using any of the embodiments disclosed herein including, but not limited to, the range clone embodiments depicted in  FIGS. 3A-E , the reference entry embodiments of  FIGS. 4A-E , and/or the intermediate mapping layer embodiments of  FIGS. 5A-B . 
     The range clone, move, and/or merge operations disclosed herein may be used to implement higher-level operations, such as deduplication, snapshots, efficient file copy operations (logical file copies), file consistency management, address space management, mmap checkpoints, atomic writes, and the like. These higher-level operations may also be exposed through the interface  131  of the storage layer  130 . The disclosed operations may be leveraged by various different storage clients  106 , such as operations systems, file systems, data base services, and/or the like. 
       FIG. 9A  depicts one embodiment of a system  900 A comprising a storage layer  130  configured to implement file management operations. The system  900 A may comprise a file system  906  that may be configured to leverage functionality of the storage layer  130  to reduce complexity, overhead, and the like. The file system  906  may be configured to leverage the range clone, move, move, snapshot, deduplication, and/or other functionality disclosed herein to implement efficient file-level snapshot and/or copy operations. The file system  906  may be configured to implement such operations in response to client requests (e.g., a copy command, a file snapshot ioctrl, or the like). The file system  906  may be configured to implement efficient file copy and/or file-level snapshot operations on a source file by, inter alia, a) flushing dirty pages of the source file (if any), b) creating a new destination file to represent the copied file and/or file-level snapshot, and c) instructing the storage module  130  to perform a range clone operation configured to clone the source file to the destination file. 
       FIG. 9A  depicts various embodiments for implementing range clone operations for a file system  906 . In some embodiments, and as depicted in state  911 A, the storage layer  130  may be configured to maintain a logical address space  132  in which LIDs of the source file (the file to be cloned) are mapped to file data on the storage medium by use of the forward map  160 . The corresponding range clone operation depicted in state  911 B may comprise: a) allocating a set of LIDs for the destination file, and b) mapping the LIDs of the source file and the destination file to the file data on the storage medium  140 . The range clone operation may further comprise storing a persistent note  366  on the storage medium  140  to indicate that the file data is associated with both the source file and destination file LIDs. The range clone operation may further comprise rewriting the file data in accordance with the updated contextual format, as disclosed herein. 
     In other embodiments, the storage layer  130  may leverage a reference map  460  to implement range clone operations (e.g., as disclosed in  FIGS. 4A-E ). Before the range clone operation, in state  911 C, the LIDs of the source file may be directly mapped to the corresponding file data in the forward map  160 . Creating the range clone in state  911 D may comprise associating one or more reference entries in the reference map  460  with the file data, and linking indirect entries corresponding to the source file LIDs and the destination file LIDs to the reference entry. The range clone operation may further comprise storing a persistent note  366  on the storage medium  140  and/or updating the contextual format of the file data, as disclosed herein. 
     In some embodiments, the storage layer  130  may be configured to implement range clone operations using an intermediate layer mapping layer (e.g., as disclosed in  FIGS. 5A-B ). As indicated in state  911 E, the source file may correspond to a set of VIDs of a VAS  532 , which may be mapped to file data on the storage medium  140  through an intermediary address space (e.g., logical address space  132  of the storage layer  130 ). Performing the range clone operation may comprise: a) allocating VIDs in the VAS  532  for the destination file, and b) associating the VIS of the destination file with the LIDs of the intermediate mapping layer (e.g., the same set of LIDs mapped to the source file VIDs). The range clone operation may further comprise storing a persistent note  366  on the storage medium  140  indicating that the destination VIDs are associated with the file data LIDs. Since the file data is already bound to the intermediate identifiers, the contextual format of the file data may not need to be updated. 
     The file system  906  may be further configured to leverage the storage layer  130  to checkpoint mmap operations. As used herein, an “mmap” operation refers to an operation in which the contents of files are accessed as pages of memory through standard load and store operations rather than the standard read/write interfaces of the file system  906 . An “msync” operation refers to an operation to flush the dirty pages of the file (if any) to the storage medium  140 . The use of mmap operations may make file checkpointing difficult. File operations are performed in memory and an msync is issued when the state has to be saved. However, the state of the file after msync represents the current in-memory state and the last saved state may be lost. Therefore, if the file system  906  were to crash during an msync, the file could be left in an inconsistent state. 
     In some embodiments, the file system  906  is configured to checkpoint the state of an mmap-ed file during calls with msync. Checkpointing the file may comprise creating a file-level snapshot (and/or range clone), as disclosed above. The file-level snapshot may be configured to save the state of the file before the changes are applied. When the msync is issued, another clone may be created to reflect the changes applied in the msync operation. As depicted in  FIG. 9B , in state  913 A (prior to the mmap operation), file  1  may be associated with LIDs  10 - 13  and corresponding storage addresses P 1 -P 4  on the storage medium  140 . In response to the mmap operation, the file system  906  may perform a range clone operation through the interface  131  of the storage layer  130 , which may comprise creating a clone of file  1  (denoted file  1 . 1 ). The file  1 . 1  may be associated with a different set of LIDs  40 - 43  that reference the same file data (e.g., the same storage addresses P 1 -P 4 ). In other embodiments, file  1  may be cloned using a reference map  460  and/or an intermediate translation layer, as disclosed above. 
     In response to an msync call, the file system  906  may perform another range clone operation (by use of the storage layer  130 ). As illustrated in state  913 C, the range clone operation associated with the msync operation may comprise updating the file  1  with the contents of one or more dirty pages (storage addresses P 5  and P 6 ) and cloning the updated file  1  as file  1 . 2 . The file  1 . 1  may reflect the state of the file before the msync operation. Accordingly, in the event of a failure, the file system  906  may be capable of reconstructing the previous state of the file  1 . 
     As disclosed above, storage layer  130  may be configured to implement range clone and range merge operations, which may be leveraged to implement higher-level operations such as file consistency (e.g., close-to-open file consistency, as disclosed in further detail herein), atomic operations, and the like. These operations may comprise: a) cloning a particular region of the logical address space  132 , b) performing storage operations within the cloned region, and c) selectively merging and/or folding the cloned region into another portion of the logical address space  132 . As used herein, merging and/or folding regions of the logical address space  132  refers to combining two or more LID ranges by, inter alia, incorporating changes implemented in one of the ranges into one or more other ranges. A merge operation may be implemented according to a merge policy, which may be configured to resolve conflicts between different LID ranges. The merge policy may include, but is not limited to, an “overwrite” mode, in which the contents of one of one LID range “overwrites” the contents of another LID range; an “OR” mode, in which the contents of the LID ranges are combined together (e.g., in a logical OR operation); a copy-on-conflict mode in which conflicts are resolved by creating separate independent copies of one or more LID ranges; and/or the like. In the overwrite mode, the LID range that overwrites the contents of the one or more other LID ranges may be determined based on any suitable criteria including, but not limited to, commit time (e.g., more recent operations overwrite earlier operations), priority, and/or the like. 
       FIG. 9C  depicts embodiments of range merge operations implemented by use of the storage layer  130 . In the  FIG. 9C  embodiment, the storage layer  130  may be configured to clone the identifier range  914 , which may be represented by one or more entries within the forward map  160 . The LIDs  072 - 083  within the range  914  may be bound to storage addresses  95 - 106 . The range clone and/or merge operations disclosed herein may be implemented using any of the range clone and/or move embodiments of  FIGS. 3A-E , the reference entry embodiments of  FIGS. 4A-E , and/or the intermediate mapping layer embodiments of  FIGS. 5A-B . Accordingly, in some embodiments, the LIDs  072 - 083  may be bound to the storage addresses  95 - 106  through one or more reference entries and/or intermediate mapping layers. 
     The storage layer  130  may be configured to clone the range  914 , which, as illustrated at state  941 A, may comprise binding a new range of LIDs  924  to the storage addresses  95 - 106 . The ranges  914  and/or  924  may comprise respective metadata  984  and/or  994  configured to indicate that the ranges  914  and  924  are related (e.g., bound to the same set of storage addresses). The metadata  984  and/or  994  may be configured to link the LIDs  072 - 083  to  972 - 983  such that modifications pertaining to one of the LID ranges can be correlated to LIDs in the other range (e.g., data written in association with LID  972  can be associated with the corresponding LID  072 , and so on). The metadata  984  and/or  994  may indicate a synchronization policy for the cloned LID ranges which, as disclosed above, may indicate whether allocation operations between clones are to be synchronized. The metadata  984  and/or  994  may further comprise and/or reference a merge policy, which may specify how merge conflicts are to be managed. The merge policy may be specified through the interface  131  of the storage layer  130 , may be determined based on a global and/or default merge policy, may be specified through request parameters (e.g., fadvise, ioctrl, etc.), and/or the like. The clone operation may further comprise appending a persistent note  366  to the storage medium  140  that is configured to associate the data at storage addresses  95 - 106  with the LID range  972 - 983  (and/or rewriting the data in an updated contextual format), as disclosed above. 
     The storage layer  130  may perform storage operations within one or more of the ranges  914  and/or  924  in response to storage requests from one or more storage clients  106 . As illustrated in state  941 B, a storage operation may modify data associated with the LIDs  972 - 973 , which may comprise associating the identifiers  972 - 973  with a new set of storage addresses  721 - 722 . Following the storage operation(s) of state  941 B, the storage layer  130  may perform a range merge operation to merge the LID range  972 - 983  with the range  072 - 083 . The range merge operation may comprise incorporating the modifications made in reference to the LID range  924  into the LID range  914  in accordance with a merge policy. The merge policy may specify that modifications made in the cloned range  924  overwrite data within the source range  914 . Accordingly, the result of the merge operation illustrated in state  941 C may comprise binding LIDs  072 - 073  of the source range  914  to the modified data at storage addresses  721 - 722 . The range merge operation may further comprise deallocating the cloned LID range  972 - 983 , storing a persistent note  366  configured to associate the data at storage addresses  756 - 757  with LIDs  072 - 073 , and/or rewriting the data at storage addresses  721 - 722  in an updated contextual format, as disclosed herein. Data stored at storage addresses  95 - 96  that has been obviated by the new data at  721 - 722  may be invalidated, as disclosed above. 
     Storage operations performed within the ranges  914  and/or  924  may result in conflicts. In some embodiments, the merge policy associated with the LID ranges may preempt conflicts. As disclosed in further detail herein, in an atomic storage operation, the storage layer  130  may lock one or more LID ranges while atomic storage operations are completed in one or more corresponding ranges. In other implementations, however, the storage layer  130  may allow storage operations to be performed concurrently within cloned ranges. In state  941 D, the storage layer  130  may implement storage operation(s) configured to overwrite and/or modify data associated with the LIDs  972 - 973  and  982 - 983  in the range  924 . The storage layer  130  may implement other storage operation(s) configured to overwrite and/or modify data associated with LIDs  072 - 073  of range  914 . The storage operation(s) pertaining to the LIDs  072 - 073  and  972 - 973  may create a merge conflict between the ranges  914  and  924 . The merge conflict may be resolved according to a merge policy, as disclosed above. In some embodiments, the merge policy may comprise applying the most recent modification, based on, inter alia, the relative order of the storage operations in the storage log. In other implementations, the merge policy may resolve conflicts based on relative priority of the storage clients  106  (processes, applications, and/or the like) that requested the respective storage operations. In another implementation, the merge policy may resolve conflicts by creating two (or more) versions of the ranges  914  and/or  924  to represent the different, conflicting versions. 
     State  941 E depicts one embodiment of a result of a merge operation configured to incorporate the operations operation(s) associated with LIDs  072 - 073  instead of the conflicting modifications associated with LIDs  972 - 973 . Therefore, in state  941 E, the LIDs  072 - 073  are bound to the storage addresses  756 - 757  corresponding to the storage operation(s) performed in reference to the LIDs  072 - 073 , rather than storage addresses  721 - 722  corresponding to the storage operation(s) performed in reference to the LIDs  972 - 973 . 
     State  941 F depicts one embodiment of a result of a merge operation configured to incorporate the modifications of the range  972 - 973  instead of the conflicting modifications made in reference to the LIDs  072 - 073 . Accordingly, in state  941 F, the identifiers  072 - 073  are bound to the storage addresses  721 - 722  corresponding to the storage operation(s) performed in reference to the LIDs  972 - 973 , rather than the storage addresses  756 - 757  associated with the LIDs  072 - 073 . 
     State  941 G depicts one embodiment of a result of a merge operation configured to manage merge conflicts by creating separate range copies or versions. The range  914  may incorporate the non-conflicting modifications made in reference to identifiers  982 - 983  and may retain the result of the conflicting storage operations pertaining to identifiers  072 - 073  (rather than incorporating storage addresses  721 - 722 ). The other LID range  924  may retain the modifications of state  941 D without incorporating the results of the conflicting storage operation(s) made in reference to identifiers  072 - 073 . Although state  941 G depicts the copies using the original cloned LID ranges  072 - 083   914  and  974 - 981   924 , the disclosure is not limited in this regard and could be configured to create the range copies and/or versions within any region of the logical address space  132 . The range merge operations disclosed in reference to states  941 E-G may further comprise appending one or more persistent notes  366  to the storage medium  140  to associate the data stored at storage addresses  721 - 722 ,  756 - 757 , and/or  767 - 768  with the corresponding LIDs and/or rewriting the data in one or more background storage operations, as disclosed herein. 
     In some embodiments, operations within one or more of the cloned LID ranges  914  and/or  924  may comprise modifying the LID ranges  914  and/or  924  by, inter alia, expanding the ranges  914  and/or  924 , contracting the ranges  914  and/or  924 , or the like. Extending one of the ranges  914  and/or  924  may comprise a corresponding extension to the other range, and, as such, allocation operations may be predicated on allocating additional LID (s) in both ranges  914  and  924 . 
     The range merge operations disclosed herein may be implemented using any of the range clone and/or move embodiments of  FIGS. 3A-E , the reference entry embodiments of  FIGS. 4A-E , and/or the intermediate mapping embodiments of  FIGS. 5A-B .  FIG. 9D  depicts an embodiment of a range merge operation using a reference map  460 . As depicted in state  943 A, cloning the range  914  may comprise allocating a LID range  924  in the logical address space  132 , linking the ranges  914  and  924  (using, inter alia, metadata  984  and/or  994 ), and associating the ranges  914  and  924  with the reference identifiers  934  in the reference map  460 . The range clone operation may further comprise storing a persistent note  366  on the storage medium  140  configured to associate the range  934  in the reference map  460  with the indirect ranges  914  and/or  924 , as disclosed above. The range  934  within the reference map  460  may be bound to the storage addresses  95 - 106 . Accordingly, both ranges  914  and  924  may indirectly reference the same data at the same storage addresses. 
     A storage operation within the range  924  configured to modify data corresponding to LIDs  982 - 983  may comprise allocating new LIDs within the range  924  and binding the new local entry  982 - 983  to the corresponding storage addresses  767 - 768 , as depicted in state  943 B. Merging the ranges  914  and  924  may comprise incorporating the modified data at storage addresses  767 - 768  into the range  914  in accordance with a merge policy, as disclosed above. In the  FIG. 9D  embodiment, the range merge operation of state  943 C may comprise removing the reference entry  934  and updating the LIDs  081 - 083  of range  914  to reference the updated data at storage addresses  767 - 768 . The merge operation may further comprise storing a persistent note  366  and/or rewriting the data at storage addresses  767 - 768  in an updated contextual format, as disclosed above. 
       FIG. 9E  depicts further embodiments of range clone and range merge operations implemented by the storage layer  130 .  FIG. 9E  illustrates range clone and range merge operations in embodiments comprising an intermediary address space, as disclosed in conjunction with  FIGS. 5A-B . In state  947 A, the VID range  914  comprising VIDs  072 - 083  are indirectly bound to storage addresses  95 - 106  through intermediary identifiers  272 Z- 283 Z in the VAS forward map  560 . The intermediary identifiers may be part of a separate, intermediate address space  2136  (e.g., the logical address space  132  of the storage layer  130 ). 
     As illustrated in state  947 B, cloning the VID range  914  may comprise allocating a new VID range  924  comprising VIDs  972 - 983  and associating the range  924  with the intermediary identifiers  272 Z- 283 Z in the VAS forward map  560 . The clone operation may further comprise storing a persistent note  366  on the storage medium  140  that is configured to associate the VID range  924  with the intermediary addresses  272 Z- 283 Z. Storage operations may be performed in reference to the VID ranges  914  and/or  924 , as disclosed herein. Modifications to the VID ranges  914  and/or  924  may be reflected in updated mappings between the respective VID ranges  914  and/or  924  and the intermediate address space  2136 . In state  947 C, a storage operation modifying data of VIDs  982 - 983  is reflected in updated mappings between VIDs  982 - 983  and intermediate identifiers  984 Z- 985 Z, and storage addresses  456 - 457 . Merging the VID ranges  914  and  924  may comprise updating the VID mappings of range  914  to reference the updated data (through the intermediary addresses  984 Z- 985 Z), as illustrated in state  947 D. The merge operation may further comprise resolving merge conflicts (if any), as disclosed above. The merge operation may further comprise appending one or more persistent notes  366  to the storage medium  140  to associate the VIDs  082 - 083  with the intermediate addresses  984 Z- 985 Z. 
     In some embodiments, the storage layer  130  may leverage the range clone, move, and/or merge operations disclosed herein to provide file consistency functionality for storage clients  106 , such as file systems, databases, and/or the like. Referring to  FIG. 9F , a file system  906  may leverage the storage layer  130  to implement a close-to-open file consistency model per the Network File System (NFS) version 3 protocol and/or other file system implementations and/or protocols. The close-to-open file consistency model may be configured to allow multiple processes and/or applications (file system clients) to operate on the same file concurrently. File modifications are committed at the time the file is closed; other clients operating on the file in parallel do not see the changes until the next time the file is opened. Accordingly, the state of the file is set at the time the file is opened and changes implemented in parallel by other clients are not applied until the file is re-opened. 
     In some embodiments, the file system  906  may leverage the storage layer  130  to preserve the “original” data of the file (e.g., a consistent version of the file) while modifications are made within the working, cloned range. As used herein, preserving the “original” data of the file and/or a consistent version of the file refers to maintaining the file data in a state corresponding to the time the file was opened and/or keeping a log of file modifications from which the state of the file data in its original, unmodified state can be reconstructed. 
       FIG. 9F  depicts one embodiment of a system  900 F comprising storage layer  130  configured to implement a close-to-open file consistency model. The file system  906  (and/or other storage client(s)  106 ) may leverage the storage layer  130  to efficiently implement close-to-open file consistency. The storage layer  130  may be configured to: a) clone files in response to file open requests of the file system clients  926 A-N, resulting in a “primary” or “consistent” version of the file and a “working” version of the file; b) perform storage operations in reference to the working version of the file; and c) merge the working version of the file into the primary version of the file in response to file closure. The storage layer  130  may be configured to clone the file data in one or more range clone operations, as disclosed herein (e.g., using the range clone embodiments of  FIGS. 3A-E ,  4 A-E,  5 A-B, and/or the like). The storage layer  130  may be further configured to merge the working version of the file and the primary or consistent version of the file using one or more range merge and/or fold operations, as disclosed herein. The working version of the file may represent the state of the file at the time the file was opened by a particular storage client  926 A-N. The storage client  926 A-N may have exclusive access to the working version of the file, and, as such, the working version of the file may be isolated from file modifications made by other clients  926 A-N. The storage layer  130  may be configured to maintain the original, unmodified file data in reference to the “primary” or “consistent” logical interface of the file, which may comprise maintaining the associations between the file data and the consistent logical interface while storage operations are performed in reference to the working logical interface of the file. Conflicts between file modifications made by different storage clients  926 A-N may be resolved according to conflict resolution policy or merge policy, such as last write (e.g., last write in time overwrites previous writes); copy on conflict (e.g., create separate versions of the file); priority based on client  926 A-N, application, process, and/or the like; and so on. 
     In the  FIG. 9F  embodiment, at state  953 A, the translation module  134  comprises mappings  951 A between the LIDs of a file (file LIDs  950 A) and data of the file  952 A on the storage medium  140  at storage addresses P 0 -P 3 . The mappings  951 A may be implemented using the forward map  160  disclosed herein and/or one or more intermediate mapping layers as disclosed in conjunction with  FIGS. 5A-B . 
     In state  953 B, the storage layer  130  may be configured to clone the file in response to a file open request of a storage client (storage client  926 B). The request may be received through the interface  131  as an explicit request, a request parameter (e.g., fadvise, ioctrl, etc.), and/or the like. The clone operation may comprise one or more range clone operations, which, as disclosed herein, may comprise allocating a new set of “cloned” file LIDs  950 B corresponding to the working version file and associating the set of cloned identifiers  950 B with the same file data  952 A as the LIDs  950 A of the primary version of the file (the original, or consistent set of logical identifiers  950 A). The range clone operation may further comprise storing a persistent note  366  on the storage medium  140  to associate the file data  952 A with both the primary file LIDs  950 A and the working version of the file LIDs  950 B, as disclosed above. 
     In some embodiments, the storage layer  130  and/or file system  906  may be configured to direct file operations performed by the storage client  926 B to the working version of the file (the working set of LIDs  950 B). Accordingly, modifications made by the storage client  926 B may be made in reference to the cloned file LIDs  950 B. Such modifications may not affect the state of the original, primary version of the file LIDs  950 A. Therefore, the storage client  926 B may modify the working version of the file in reference to the LIDs  950 B without changing the LIDs  950 A of the original, primary version of the file. 
     In state  953 C, the storage client  926 B has performed a storage operation (through the storage layer  130 ) to modify data of the file stored at storage address P 3 ; the modified data may be appended to the storage log at storage address P 64 . In response, the translation module  134  may update mappings  951 B to bind the LIDs of the cloned, working version of the file  950 B to the modified file data  952 B at storage address P 64 . Other LID(s) not modified by the storage client  926 B may continue to be bound to the original, unmodified file data  952 A. The storage layer  130  is configured to preserve the original mappings  951 A between the identifiers  950 A of the primary version of the file and the unmodified file data  952 A at storage addresses P 0 - 3 . 
     Another storage client  926 N may issue a request to open the file before the storage client  926 B has closed the file. In response, and as depicted in state  953 D, the storage layer  130  may create another clone of the primary file (clone the primary file identifiers  950 A). The cloned LIDs (FIDs  950 C) may correspond to the original state of the file without the modifications made by storage client  926 B in reference to the cloned identifier range  950 B. Accordingly, the cloned LIDs  950 C may be mapped  951 C to the original, unmodified file data  952 A at storage addresses P 0 - 3 . The storage client  926 N may perform storage operations in reference to the new cloned file identifier range  950 C in parallel with the storage client  926 B. Changes made by the clients  926 B and  926 N may be isolated within their respective LID ranges  950 B and  950 C, and, as such, may not be applied to the primary version of the file (LIDs  950 A and/or one another). 
     State  953 E illustrates the result of the storage client  926 B closing the file. In response to a request to close the file of storage client  926 B, the storage layer  130  may be configured to merge the contents of the corresponding range (FIDs  950 B) into the primary version of the file (LIDs  950 A) in one or more range merge operations. The changes may not, however, be merged into the version of the file in use by storage client  926 N (FIDs  950 C); the storage client  926 N may not have access to the modifications until the client  926 N re-opens the file. Incorporating the modifications may comprise one or more range merge operations, as disclosed herein. The range merge operations may be configured to merge the modifications made in reference to the cloned LID range  950 B into the LID range  950 A of the primary version of the file. In the  FIG. 9F  embodiment, the range merge operation comprises updating the mappings  951 A of the primary file LIDs  950 A to reference the modified file data  952 B at storage address P 64 . The data that was not modified by the client  924 B may remain bound to the original, unmodified file data  952 A at P 0 - 3 . 
     As disclosed herein, in some embodiments, the modified file data  952 B may include persistent metadata configured to associate the modified file data  952 B at storage address P 64  with one or more of the LIDs  950 B (as opposed to the LIDs  950 A associated with the primary version of the file). The range merge operation may, therefore, further comprise appending a persistent note  366  to the storage medium  140  configured to associate one or more of the range of LIDs  950 A with the modified file data  952 B at storage address P 64 . The data at storage address P 64  may be rewritten with updated persistent metadata in one or more background operations. Following the file close operation (and corresponding range merge operations), the translation module  134  may be configured to deallocate the LIDs of range  950 B. 
     The client  926 N may modify the file in reference to the cloned file identifiers  950 C. As depicted in state  953 F of  FIG. 9G , the storage client  926 N may perform one or more operations that conflict with the modifications implemented by the client  926 B. The modifications may occur before the client  950 B has closed the file (before the modifications of client  926 B have been applied to the LIDs  950 A of the primary version of the file as in state  953 E). As such, the LIDs  950 A are mapped  951 A to the original, unmodified file data  952 A, one or more of the identifiers of the range  950 B allocated to storage client  926 B are mapped to modified file data  952 B, and one or more of the identifiers of range  950 C allocated to storage client  926 N are mapped to conflicting file data  952 C. The LIDs  950 B and  950 C that correspond to unmodified data may continue to reference the original, unmodified file data  952 A. 
     The clients  926 B and  926 C may eventually close their respective files, which may comprise merging the modifications made in reference to the respective LID ranges  950 B and  950 C into the range  950 A of the primary version of the file. The storage layer  130  may be configured to resolve conflicts between the ranges  950 B and  950 C according to a merge policy  944 . In some embodiments, the merge policy  944  may be based on the order in which the storage clients  926 B and  926 C closed the files; the modifications of the last file closed may overwrite previously applied modifications (e.g., the modifications may be serialized). As illustrated in state  953 G, the storage client  950 B may issue the file close request before the storage client  950 C. After the client  950 B closes the file, the storage layer  130  may merge modifications made in reference to the range  950 B into the range  950 A of the primary version of the file (as illustrated, in state  953 E of  FIG. 9F ). Closure of the file by client  926 C may result in overwriting some of the modifications made by storage client  950 B (modified data  952 B) with data  952 C, as illustrated in state  953 G of  FIG. 9G . The data at P 3  and P 64  may be marked for removal from the storage medium  140  since it is no longer referenced by the primary file or a current, working version of the file. As disclosed above, the storage layer  130  may be configured to implement other merge policies, such as a priority based merge policy  944 . A priority based merge policy may resolve conflicts based on relative priorities of the storage clients  926 B and/or  926 C. In state  953 H, the storage client  926 C may close the file after the storage client  926 B; however, the modifications of storage client  926 B may be retained due to the merge policy  944  indicating that the modifications of storage client  926 B have a higher priority than conflicting modifications of storage client  926 C. Accordingly, the LIDs  950 A of the primary version of the file may continue to reference the modified file data  952 B of storage client  926 B, and the conflicting file data of storage client  926 C (data  952 C at P 96 ) may be marked for garbage collection along with the obsolete file data  952 A at P 3 . In other embodiments, the merge policy  944  may comprise a copy-on-conflict policy that results in creating two primary versions of the file. In such embodiments, and as illustrated in state  953 I, the storage layer  130  may be configured to incorporate the modifications of storage client  926 B into the primary file (using primary file LIDs  950 A), and may incorporate the conflicting modifications of storage client  926 C into a new version of the file (file identifiers  950 D). 
     Although particular embodiments of a merge policy  944  are described herein, the disclosure is not limited in this regard and could implement and/or incorporate any suitable merge policy  944 . The merge policy  944  may be implemented within the storage layer  130  and/or file system  906 . In some embodiments, the merge policy  944  of the storage layer  130  and/or file system  906  may be configured through the interface  131  of the storage layer  130 . The merge policy  944  may apply to all file operations performed through the storage layer  130 . Alternatively, or in addition, the merge policy  944  may be set on a per-file and/or per-conflict basis through, inter alia, file system API calls, fadvise, ioctrl, and/or the like, as disclosed above. 
     The storage layer  130  may be further configured to implement efficient atomic storage operations.  FIG. 10A  is a block diagram of one embodiment of a system  1000 A comprising a storage layer  130  configured to implement atomic storage operations. As used herein, an atomic storage operation refers to a storage operation that is either fully completed as a whole or is rolled back. Accordingly, atomic storage operations may not be partially completed; the storage layer  130  may be configured to invalidate and/or remove data of incomplete atomic storage operations. Implementing atomic storage operations, and particularly atomic storage operations comprising multiple steps and/or pertaining to multiple different identifier ranges or I/O vectors, may impose high overhead costs. For example, some database systems implement atomic storage operations using multiple sets of redundant write operations. 
     The storage layer  130  may comprise a transaction module  1036  configured to implement storage transactions. The transaction module  1036  may comprise an atomic storage module  1035  to leverage the range clone, range move, and/or other operations disclosed herein to increase the efficiency of atomic storage operations. In some embodiments, the interface  131  provides APIs and/or interfaces for performing vectored atomic storage operations. A vector may be defined as a data structure, such as: 
     
       
         
           
               
             
               
                   
               
             
            
               
                 struct iovect { 
               
            
           
           
               
               
            
               
                  uint64 iov_base; 
                 // Base address of memory region for input or output 
               
               
                  uint32 iov_len; 
                 // Size of the memory referenced by iov_base 
               
               
                  uint64 dest_lid; 
                 // Destination logical identifier 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     The iov_base parameter may reference a memory or buffer location comprising data of the vector, iov_len may refer to a length or size of the data buffer, and dest_lid may refer to the destination logical identifier(s) for the vector (e.g., base logical identifier with the length of the range being implied and/or derived from the input buffer iov_len). 
     A vector storage request to write data to one or more vectors may, therefore, be defined as follows: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                   
                 vector_write ( 
               
               
                   
                   
                  int fileids, 
               
               
                   
                   
                  const struct iovect *iov, 
               
               
                   
                   
                  uint32 iov_cnt, 
               
               
                   
                   
                  uint32 flag) 
               
               
                   
               
            
           
         
       
     
     The vector write operation above may be configured to gather data from each of the vector data structures referenced by the *iov pointer and/or specified by the vector count parameter (iov_cnt) and write the data to the destination logical identifier(s) specified in the respective iovect structures (e.g., dest_lid). The flag parameter may specify whether the vector write operation should be implemented as an atomic vector operation. 
     As illustrated above, a vector storage request may comprise performing the same operation on each of a plurality of vectors (e.g., implicitly perform a write operation pertaining to one or more different vectors). In some embodiments, a vector storage request may specify different I/O operations for each constituent vector. Accordingly, each iovect data structure may comprise a respective operation indicator. In some embodiments, the iovect structure may be extended as follows: 
     
       
         
           
               
             
               
                   
               
             
            
               
                 struct iovect { 
               
            
           
           
               
               
            
               
                  uint64 iov_base; 
                 // Base address of memory region for input or output 
               
               
                  uint32 iov_len; 
                 // Size of the memory referenced by iov_base 
               
               
                  uint32 iov_flag; 
                 // Vector operation flag 
               
               
                  uint64 dest_lid; 
                 // Destination logical identifier 
               
               
                 } 
               
               
                   
               
            
           
         
       
     
     The iov_flag parameter may specify the storage operation to perform on the vector. The iov_flag may specify any suitable storage operation, which includes, but is not limited to, a write, a read, an atomic write, a trim or discard request, a delete request, a format request, a patterned write request (e.g., request to write a specified pattern), a write zero request, or an atomic write operation with verification request, allocation request, or the like. The vector storage request interface described above may be extended to accept vector structures: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                   
                 vector_request( 
               
               
                   
                   
                  int fileids, 
               
               
                   
                   
                  const struct iovect *iov, 
               
               
                   
                   
                  uint32 iov_cnt, 
               
               
                   
                   
                  uint32 flag) 
               
               
                   
               
            
           
         
       
     
     The flag parameter may specify whether the vector operations of the vector_request are to be performed atomically. Further embodiments of atomic storage operations are disclosed in U.S. patent application Ser. No. 13/725,728, entitled, “Systems, Methods, and Interfaces for Vector Input/Output Operations,” filed on Dec. 21, 2012 for Ashish Batwara et al., and which is hereby incorporated by reference. 
     The transaction module  1036  may comprise an atomic storage module  1035  configured to implement atomic storage operations within the storage layer  130 . The atomic storage module  1035  may be configured to implement storage operations of an atomic storage request in reference to a different set of identifiers than the target or destination identifiers of the request. After the atomic storage operations are complete, the atomic storage module  1035  may be configured to move the data to the respective target or destination identifier(s) of the atomic storage request, as disclosed herein. 
     In some embodiments, the atomic storage module  1035  implements atomic storage operations directed to a first set of logical identifiers in reference to a second set of identifiers. The second set of identifiers may be considered to be ephemeral, temporary, working, or in-process identifiers. The second set of identifiers may not be directly accessible to storage clients  106 . The second set of identifiers may correspond to a particular region of the logical address space  132 , a particular virtual address space (e.g., a VAS  532 ), a separate namespace, and/or the like. After completing the storage operations of the atomic storage request, the atomic storage module  1035  may implement a range move operation configured to associate data of the atomic storage request with the first set of identifiers. The data may be dis-associated from the second set of identifiers. As above, the second set of identifiers may be distinguishable from LIDs of the logical address space  132  and/or VIDs of a VAS  532 . In the event of a failure condition, the reconstruction module  1037  may identify data bound to such identifiers as pertaining to failed transactions (e.g., incomplete atomic storage operations). The identified data may be invalidated during metadata reconstruction operations and/or corresponding entries may be omitted from the storage metadata  135  (e.g., omitted from the forward map  160 , VAS forward map  560 , reference map  460 , and/or the like). 
     In some embodiments, the atomic storage module  1035  implements atomic storage operations within a separate address space, such as the transaction address space  1032  of  FIG. 10A . Although  FIG. 10A  describes use of a transaction address space  1032  the disclosure is not limited in this regard, and could be adapted to use any suitable address range and/or namespace including, but not limited to, a portion of the logical address space  132  (e.g., a range, extent, and/or set of LIDs), a portion of a VAS  532 , a reference map  460 , an intermediate address space, and/or the like. The identifiers of the transaction address space  1032  (transactional identifiers) may not be directly accessible to the storage clients  106 . 
     The atomic storage module  1035  may perform atomic storage operations in reference to the transaction address space  1032 , and, after the atomic storage operations are complete, may perform an atomic range move operation configured to move data of the atomic storage operations from the transaction address space  1032  into the logical address space  132  (or other destination or target namespace, such as a particular VAS  532 ). The atomic range move operation may include updating bindings within the forward map  160 , writing metadata to the storage medium  140  (e.g., appending a persistent note  366  to the log), and/or the like, as disclosed herein. 
     In the  FIG. 10A  embodiment, a storage client  106  issues an atomic storage request pertaining to vectors  1040 A and  1040 B within the logical address space  132 . As illustrated in  FIG. 10A , the vectors  1040 A and  1040 B may correspond to existing entries within the forward map  160 . Before the atomic storage operation is implemented (at state  1015 A), the LIDs  10 - 13  of vector  1040 A may be bound to storage addresses P 1 -P 4  and the LIDs  36 - 38  of vector  1040 B may be bound to storage addresses P 6 - 8 . In other embodiments, the atomic storage request may pertain to LIDs that are not allocated and/or are not yet bound to storage addresses and, as such, do not have corresponding entries within the forward map  160  (and/or other mapping layers). 
     In response to the atomic storage request, the atomic storage module  1035  may access a second set of identifiers within the transaction address space  1032 , by use of, inter alia, a redirection module  1034 . The redirection module  1034  may be configured to allocate the second set of identifiers within the transactional address space  1032 . The transactional identifiers may be used to implement portions of the atomic storage request (e.g., track in-process portions of the atomic storage operations). The redirection module  1034  may be further configured to link the second set of identifiers to the first set of LIDs (e.g., the target LIDs of the atomic storage request) by use of, inter alia, the storage metadata  135 , entries within the forward index  160  and/or other index metadata, and/or the like. In some embodiments, the atomic storage module  1035  may be further configured to perform range clone operation(s) configured to bind the second set of identifiers to the same storage addresses as the first set of identifiers (vectors  1040 A and  1040 B), as disclosed herein. 
     As illustrated in state  1015 B, the redirection module  1034  may allocate a second set of identifiers comprising vectors  1042 A and  1042 B, which include transactional identifiers Z 0 - 3  and Z 6 - 8 . Bindings between transactional identifiers and storage locations may be maintained in a the storage metadata using, inter alia, an intermediate mapping layer, such as the transaction map  1060 . The transaction map  1060  may comprise mappings between transactional identifiers and LIDs of the logical address space  132  (and/or VIDs of a VAS  532 ). In the  FIG. 10A  embodiment, the transaction map  1060  comprises links  1064 A between the transactional identifiers of vector  1042 A and corresponding LIDs of vector  1040 A (LIDs  10 - 13 ), the transaction map  1060  further includes links  1064 B between the transactional identifiers of vector  1042 B and LIDs  36 - 38  of vector  1040 B. The transaction map  1060  may further include bindings between transactional identifiers and storage locations. State  1015 B depicts range clone operation(s) in the transaction map  1060 , including bindings  1062 A between transactional identifiers  1042 A and the storage locations P 1 - 4  of the LIDs in vector  1040 A, and bindings  1062 B between transactional identifiers  1042 B and the storage locations P 6 - 8  of the LIDs in vector  1040 B. 
     The atomic storage module  1035  may implement atomic storage operations of the atomic storage request within the transaction address space  1032 , which may comprise redirecting storage operations from the first set of LIDs (vectors  1040 A and/or  1040 B) to the second set of identifiers (the transactional identifiers of  1042 A and  1042 B). Redirecting the storage operations may comprise translating references to LIDs in the atomic storage request to the second set of transactional identifiers by use of, inter alia, the transaction map  1060 . For example, a storage operation pertaining to LID  10  may be redirected to transactional identifier Z 0  based on the mappings  1064 A of the transaction map  1060 . Storage operations configured to allocate logical capacity may be redirected to (and maintained within) the transactional address space  1032 . For example, a request to extend the vector  1040 A to include LIDs  14 - 20  may comprise: a) allocating the LIDs in the logical address space  132 , b) allocating corresponding transactional identifiers in the transactional address space  1032 , and c) linking the allocated transactional identifiers and LIDs in the transaction map  1060 . A request to TRIM LIDs may comprise marking the corresponding identifiers as invalid in the transaction map  1060 . The corresponding LIDs in the logical address space  132  may be TRIMed in response to the range move operation performed upon completion of the atomic storage operations, as disclosed in further detail herein. 
     As illustrated in state  1015 C, the storage operations of the atomic storage request may comprise appending data to the storage medium  140  at storage locations P 9 - 13  and P 100 - 102 . The corresponding storage operations may be redirected to the transactional address space  1032 , as disclosed herein. Accordingly, the data of the atomic storage request may be associated with the transactional identifiers Z 0 - 3  and Z 6 - 8 , which may comprise: a) binding the storage locations P 9 - 13  and P 100 - 102  to the transactional identifiers Z 0 - 3  and Z 6 - 8  in the transaction map  1060 , and b) storing the data at P 9 - 13  and P 100 - 102  with persistent metadata  114  configured to associate the data with respective transactional identifiers Z 0 - 3  and Z 6 - 8 . 
     Other storage operations may be performed concurrently with and/or interleaved within the atomic vector operations. Accordingly, data of the atomic storage request need not be stored at contiguous storage locations within the storage address space  144  of the storage medium  140 . Data of the atomic storage request may be distinguished from other data that is not related to the atomic storage request based on, inter alia, the bindings between the data at storage locations P 9 - 10  and P 100 - 102  and the transactional identifiers Z 0 - 3  and Z 6 - 8 . 
     As further illustrated at state  1015 C, the original, unmodified state of the LIDs in vectors  1040 A and  1040 B may be unchanged while the atomic storage operation(s) are in progress; the data at storage locations P 1 - 4  and P 6 - 8  may remain on the storage medium  140 , and the bindings between the original, unmodified data and the LIDs  10 - 13  and  36 - 38  may be maintained within the forward index  160 . Therefore, the original, unmodified data corresponding to the vectors  1040 A and  1040 B may be maintained in a consistent state while the atomic storage operation(s) are being performed, and may be preserved regardless of failures in the atomic storage operation (s). 
     Completion of the atomic storage operation may comprise merging the contents of the transactional address space  1032  into the logical address space  132 . As illustrated in state  1015 D, after completing the atomic storage operations in the transactional address space (as shown in state  1015 C), the atomic storage module  1035  may perform a range move operation to modify the logical interface of the data at P 9 - 13  and P 100 - 102  to bind the data to the first set of LIDs (the destination LIDs of vectors  1040 A and  1040 B). The range move operation may comprise updating the forward map  160  to associate LIDs  10 - 13  of vector  1040 A with storage locations P 9 - 13  and to associate LIDs  36 - 38  of vector  1040 B with storage locations P 100 - 102 . The range move operation may further comprise storing a persistent note  366  on the storage medium  140  to bind the storage address P 9 -P 13  to LIDs  10 - 13  and P 100 - 102  to LIDs  36 - 38 , as disclosed herein. The range move operation may be implemented in other ways including, but not limited to, the reference entry embodiments of  FIGS. 4A-E  and/or the intermediary mapping embodiments of  FIGS. 5A-B . The range move operation may also include rewriting the data in a contextual format that is consistent with the updated logical interface, which may comprise rewriting the data with persistent metadata  114  configured to associate the data with the first set of LIDs (e.g., LIDs  10 - 13  and/or  36 - 38  of the logical address space  132 , respectively). The data may be rewritten in one or more background operations, as disclosed herein. 
     The atomic storage module  1035  may be configured to acknowledge completion of the atomic storage request in response to completion of the range move operation. Accordingly, completion may be acknowledged in response to storing the persistent note  366  and/or placing the persistent note  366  in a write buffer (and/or a power-cut safe domain of the storage device  141 ). Completion of the atomic storage request may further comprise deallocating the transactional identifiers used to implement the atomic storage request. 
     In some embodiments, the range move operation may further comprise modifying LID allocations within the logical address space  132 . As disclosed above, an atomic storage operation may comprise a request to allocate LIDs within the logical address space  132 . Implementing such an operation may include: a) allocating the requested LIDs (or alternative LIDs) within the logical address space  132 , b) allocating corresponding transactional identifiers in the transactional address space  1032 , and c) linking the LIDs to the transactional identifiers, as disclosed herein. The range move operation may comprise removing the transactional identifiers and/or moving data associated with the corresponding transactional identifiers to the allocated LIDs, as disclosed herein. Implementing an operation to TRIM one or more LIDs may comprise marking the corresponding transactional identifier(s) as invalid in the transaction map  1060 . The corresponding range move operation may comprise TRIMing the LIDs mapped to the transactional identifiers by, inter alia, removing the LIDs form the forward index  160  and/or storing persistent metadata indicating that the LIDs have been removed. In the  FIG. 10A  embodiment, an atomic storage request comprising a request to TRIM LID  12  may comprise invalidating transactional identifier Z 2  in the transaction map  1060 . Invalidating the transactional identifier Z 2  may comprise retaining an entry representing the transactional identifier Z 2  in the transaction map  1060 , and marking the entry as invalid, deleted, TRIMed, or the like. Completing the atomic storage request may comprise: a) invalidating the LID mapped to the transactional identifier Z 2  (e.g., invalidating the entry corresponding to LID  12  in the forward map  160  and/or other storage metadata  135 ); and/or b) configuring the persistent note  366  to TRIM the LID  12  (e.g., indicate that the data at the storage location(s) bound to LID  12  do not need to be retained on the storage medium  140 ). 
     In some embodiments, the storage layer  130  may further comprise a reconstruction module  1037  configured to reconstruct the storage metadata  135  from the contents of the storage log. The reconstruction module  1037  may reconstruct the storage metadata  135  in response to a failure condition resulting in loss to and/or corruption of the storage metadata  135 . The reconstruction module  1037  may be configured to traverse physical storage locations within the storage address space  144  in a log-order (e.g., from newest to oldest or vice versa). The reconstruction module  1037  may access the persistent metadata  114  of the storage log to reconstruct, inter alia, the LID to storage address associations of the forward map  160 . 
     In response to a failure of the atomic storage operation of  FIG. 10A , the reconstruction module  1037  may be configured to reconstruct the vectors  1040 A and  1040 B based on the contents of P 1 - 4  and P 6 - 8 , respectively. The reconstruction module  1037  may recognize that the data stored at P 9 - 13  and/or P 100 - 102  pertains to an incomplete atomic storage request based on the association of the data with the identifiers Z 0 - 3  and Z 6 - 9  of the in-process address space  1032 . The reconstruction module  1037  may, therefore, omit the entries from the forward index  160  and invalidate data at the corresponding storage locations. Alternatively, the reconstruction module  1037  may reconstruct corresponding entries in the transaction map  1060  such that the partial atomic storage request can be completed (e.g., resume from the point of failure as opposed to restarting the atomic storage operation from scratch). 
     The reconstruction module  1037  may be further configured to identify data pertaining to a completed atomic storage request. When reconstructing the storage metadata  135  after successful completion of the atomic storage request of  FIG. 10A , the reconstruction module  1037  may determine that the physical storage locations P 9 - 13  and P 100 - 102  correspond to LIDs of the logical address space  132  (and are the result of a successful atomic storage request) based on the persistent note  366  stored at storage location  109 . As disclosed above, the persistent note  366  may comprise persistent metadata configured to associate the data at P 9 - 13  and P 100 - 102  with the LIDs of vectors  1040 A and  1040 B. Accordingly, the reconstruction module  1037  may be further configured to reconstruct the associations of state  1015 C by use of the persistent note  366  regardless of whether the corresponding data has been rewritten in an updated contextual format. 
       FIG. 10B  depicts further embodiments  1000 B of atomic storage operations implemented by use of, inter alia, the storage layer  130  and aggregation layer  530  disclosed herein. At state  1017 A, an atomic storage operation pertaining to a first set of VIDs may be received. As illustrated in state  1017 A, the target VIDs of vector  4096 - 4159  may not correspond to existing VID allocation(s) and/or data. Accordingly, the VAS forward map  560  may not include entries corresponding to VIDs  4096 - 4159  and/or entries within the intermediate map  1070 . 
     As illustrated in state  1017 B, in response to the atomic storage request, the atomic storage module  1035  may be configured to allocate VIDs corresponding to the atomic storage request (entries  4096 , 64 ). If the requested entries are not available (e.g., are already allocated to another client and/or existing data), the atomic storage request may fail. Alternatively, the atomic storage module  1035  may allocate a different set of VIDs to implement the atomic storage request, which may be returned to the storage client  106  upon completion of the atomic storage request. 
     The redirection module  1034  may be configured to allocate temporary, in-process identifiers  9872 Z, 64  corresponding to the VIDs  4096 , 64 . As with the transactional identifiers disclosed herein, the in-process identifiers  9872 Z, 64  may correspond to a different namespace than the target VIDs (e.g., a transactional address space  1032 ), a particular region of the VAS  560 , a separate VAS  560 , and/or the like. The redirection module  1034  may be configured to link the VIDs  4096 , 64  to the in-process identifiers  9872 Z, 64  by use of, inter alia, metadata of respective entries within the VAS forward map  560  (and/or other storage metadata  135 ) and/or by use of a transaction map  1060  (or in-process index). Binding the transactional identifiers  9872 Z, 64  to the intermediate identifiers  1032 , 64  may comprise appending a persistent note  1066 A to the storage medium  140 . The persistent note  1066 A may comprise persistent metadata configured to associate the in-process identifiers with the intermediate identifiers  1032 , 64 . 
     In state  1017 C, the atomic storage module  1035  may be configured to implement the storage operations corresponding to the atomic storage request in reference to the in-process identifiers, which may comprise redirecting (and/or translating) VIDs of the atomic storage request to corresponding in-process identifiers. The storage operations may comprise appending data to the storage medium  140  by use of, inter alia, the log storage module  137 . The in-process identifiers  9872 Z, 64  may be bound to the appended data through the intermediate mapping layer  1070  (identifiers  1032 , 64 ) and/or the persistent note  1066 A. The data appended to the storage log may comprise persistent metadata  114  configured to bind the data of the atomic storage operation to respective intermediate identifiers  1032 , 64 . The persistent metadata  114  may further comprise a flag, or other indicator, configured to identify the data as part of an atomic storage request. 
     Completion of the atomic storage request may comprise a range move operation configured to modify the logical interface of the appended data to bind the data to the destination VIDs of the atomic storage request (VIDs  4096 , 64 ). After completing the storage operations of the atomic storage request, the atomic storage module  1035  may implement the range move operation by, inter alia: a) updating the VAS forward map  560  to associate the target VIDs  4096 , 64  with the intermediate entry  1032 , 64 ; and b) removing the mapping between the in-process identifiers  9872 Z, 64  and the intermediate entry  1032 , 64 . 
     The range move operation may further comprise deallocating the in-process identifiers  9872 Z, 64  (e.g., removing entries and/or corresponding metadata from an in-process index  1060 , as disclosed above). As illustrated in state  1017 D, the range move operation may further comprise appending another persistent note  1066 B to the storage medium  140 , which may be configured to identify the modified logical interface of the appended data. The persistent note  1066 B may bind the intermediate entry  1032 , 64  to the destination VID range  4096 , 64 . The persistent note  1066 B may further indicate that the atomic storage operation was successfully completed. The atomic storage module  1035  may be configured to acknowledge completion of the atomic storage request in response to storing the persistent note  1066 B on the storage medium  140  (and/or scheduling the persistent note  1066 B for storage within, e.g., a power-cut safe domain). 
     As disclosed above, in some embodiments, the range move operations implemented by the atomic storage module  1035  may comprise modifications to the target namespace (e.g., logical address space  132 ). In one embodiment, for example, an atomic storage request may comprise a request to TRIM an I/O vector. Implementing the atomic storage request may comprise storing a persistent note  366  within the storage log configured to TRIM a corresponding in-process or transactional identifier(s), as disclosed above. The range move operation may comprise implementing the TRIM operation within the target namespace. The TRIM operation may comprise configuring the persistent note  1066 B to TRIM the target I/O vector and/or moving the stored TRIM command to the target I/O vector, as disclosed herein. 
     The persistent note  1066 B may be used by the reconstruction module  1037  to rebuild the storage metadata  135  in the event of a failure condition, as disclosed above. The reconstruction module  1037  may rebuild the bindings of the intermediary map  1070  and/or the VAS forward map  560 . In state  1017 D, the reconstruction module  1037  may reconstruct the associations between  1032 , 64  and the corresponding storage addresses by use of the persistent metadata  114  stored with the corresponding data segments within the log (e.g., within respective packet headers). The reconstruction module  1037  may be further configured to associate the intermediate addresses  1032 , 64  with the VIDs  4096 , 64  by use of the persistent note  1066 B. 
     As illustrated in state  1017 E, the reconstruction module  1037  may identify data of a failed atomic storage operation in response to determining that a persistent note  1066 B indicating completion of the atomic storage request does not exist on the storage medium  140 . The reconstruction module  1037  may determine that the appended data was part of an incomplete, failed atomic storage request in response to identifying data that is bound to intermediate identifiers  1032 , 64  that are: a) bound to in-process identifiers  9872 Z, 64  and/or b) marked as atomic (in respective persistent metadata  114 ). In response, the reconstruction module  1037  may: a) remove and/or omit the entry  1032 , 64  from the intermediate map  1070 , b) remove and/or omit the entries  4096 , 64  and/or  9872 Z, 64  from the VAS forward map  560 , and/or c) invalidate the corresponding data on the storage medium  140 . 
       FIG. 11  is a flow diagram of one embodiment of a method  1100  for managing a logical interface of data stored in a contextual format on a non-volatile storage medium. 
     Step  1120  may comprise modifying a logical interface of data stored in a contextual format on a non-volatile storage media. The logical interface may be modified at step  1120  in response to performing an operation on the data, which may include, but is not limited to, a clone operation, a deduplication operation, a move operation, or the like. The request may originate from a storage client  106 , the storage layer  130  (e.g., deduplication module  374 ), or the like. 
     Modifying the logical interface may comprise modifying the LID (s) associated with the data, which may include, but is not limited to, referencing the data using one or more additional LIDs (e.g., clone, deduplication, etc.), changing the LID(s) associated with the data (e.g., a move), or the like. The modified logical interface may be inconsistent with the contextual format of the data on the storage medium  140 , as described above. 
     Step  1120  may further comprise storing a persistent note on the storage medium  140  that identifies the modification to the logical interface. The persistent note may be used to make the logical operation persistent and crash safe, such that the modified logical interface (e.g., storage metadata  135 ) of the data may be reconstructed from the contents of the storage medium  140  (if necessary). Step  1120  may further comprise acknowledging that the logical interface has been modified (e.g., returning from an API call, returning an explicit acknowledgement, or the like). The acknowledgement (and access through the modified logical interface at step  1130 ) occurs before the contextual format of the data is updated on the storage medium  140 . Accordingly, the logical operation may not wait until the data is rewritten and/or relocated; as disclosed herein, updating contextual format of the data may be deferred and/or implemented in a process that is outside of the “critical path” of the method  1100  and/or the path for servicing other storage operations and/or requests. 
     Step  1130  may comprise providing access to the data in the inconsistent contextual format through the modified logical interface of step  1120 . As described above, updating the contextual format of the data to be consistent with the modified contextual interface may comprise rewriting and/or relocating the data on the non-volatile storage media, which may impose additional latency on the operation of step  1120  and/or other storage operations pertaining to the modified logical interface. Therefore, the storage layer  130  may be configured to provide access to the data in the inconsistent contextual format while (or before) the contextual format of the data is updated. Providing access to the data at step  1130  may comprise referencing and/or linking to one or more reference entries corresponding to the data (via one or more indirect entries), as described above. 
     Step  1140  may comprise updating the contextual format of the data on the storage medium  140  to be consistent with the modified logical interface of step  1120 . Step  1140  may comprise rewriting and/or relocating the data to another media storage location on the storage medium  140 . As described above, step  1140  may be implemented using a process that is outside of the critical path of step  1120  and/or other storage requests performed by the storage layer  130 ; step  1140  may be implemented by another, autonomous module, such as media management module  370 , deduplication module  374 , or the like. Accordingly, the contextual format of the data may be updated independent of servicing other storage operations and/or requests. As such, step  1140  may comprise deferring an immediate update of the contextual format of the data and updating the contextual format of the data in one or more “background” processes, such as a media management process. Alternatively, or in addition, updating the contextual format of the data may occur in response to (e.g., along with) other storage operations. For example, a subsequent request to modify the data may cause the data to be rewritten out of place and in the updated contextual format. 
     Step  1140  may further comprise updating storage metadata  135  as the contextual format of the data is updated. As data is rewritten and/or relocated in the updated contextual format, the storage layer  130  may update the storage metadata  135  (e.g., forward map  160 ) accordingly. The updates may comprise removing one or more links to reference entries in a reference map  460  and/or replacing indirect entries with local entries, as described above. Step  1140  may further comprise invalidating and/or removing a persistent note from the storage medium  140  in response to updating the contextual format of the data and/or persisting the storage metadata  135 , as disclosed above. 
       FIG. 12  is a flow diagram of another embodiment of a method  1200  for managing a logical interface of data stored in a contextual format on a non-volatile storage media. The method  1200  may be implemented by one or more modules and/or components of the storage layer  130 , as disclosed herein. 
     Step  1220  comprises selecting a storage division for recovery, such as an erase block or logical erase block. As described above, the selection of step  1220  may be based upon a number of different factors, such as a lack of available storage capacity, detecting a percentage of data marked as invalid within a particular logical erase block reaching a threshold, a consolidation of valid data, an error detection rate reaching a threshold, improving data distribution, data refresh, or the like. Alternatively, or in addition, the selection criteria of step  1220  may include whether the storage division comprises data in a contextual format that is inconsistent with a corresponding logical interface thereof, as described above. 
     As disclosed above, recovering (or reclaiming) a storage division may comprise erasing the storage division and relocating valid data thereon (if any) to other storage locations on the non-volatile storage media. Step  1230  may comprise determining whether the contextual format of data to be relocated in a grooming operation should be updated (e.g., is inconsistent with the logical interface of the data). Step  1230  may comprise accessing storage metadata  135 , such as the forward map  160 , reference map  460 , and/or intermediary address space, as described above, to determine whether the persistent metadata (e.g., logical interface metadata) of the data is consistent with the storage metadata  135  of the data. If the persistent metadata is not consistent with the storage metadata  135  (e.g., associates the data with different LIDs, as described above), the flow continues at step  1240 ; otherwise, the flow continues at step  1250 . 
     Step  1240  may comprise updating the contextual format of the data to be consistent with the logical interface of the data. Step  1240  may comprise modifying the logical interface metadata to reference a different set of LIDs (and/or reference entries), as described above. 
     Step  1250  comprises relocating the data to a different storage location in a log format that, as described above, preserves an ordered sequence of storage operations performed on the non-volatile storage media. Accordingly, the relocated data (in the updated contextual format) may be identified as the valid and up-to-date version of the data when reconstructing the storage metadata  135  (if necessary). Step  1250  may further comprise updating the storage metadata  135  to bind the logical interface of the data to the new media storage locations of the data, remove indirect and/or reference entries to the data in the inconsistent contextual format, and so on, as disclosed herein. 
       FIG. 13  is a flow diagram of another embodiment of a method  1300  for managing logical interfaces of data stored in a contextual format. Step  1315  may comprise identifying duplicate data on one or more storage devices  120 . Step  1315  may be performed by a deduplication module  374  operating within the storage layer  130 . Alternatively, step  1320  may be performed by the storage layer  130  as storage operations are performed. 
     Step  1315  may comprise determining and/or verifying that the storage medium  140  comprises duplicate data (or already comprises data of a write and/or modify request). Accordingly, step  1320  may occur within the path of a storage operation (e.g., as or before duplicate data is written to the storage medium  140 ) and/or may occur outside of the path of servicing storage operations (e.g., identify duplicate data already stored on the storage medium  140 ). Step  1320  may comprise generating and/or maintaining data signatures in storage metadata  135  and using the signatures to identify duplicate data. 
     In response to identifying the duplicate data at step  1315 , the storage layer  130  (or other module, such as the deduplication module  374 ) may modify a logical interface of a copy of the data, such that a single copy may be referenced by two (or more) sets of LIDs. The modification to the logical interface at step  1320  may comprise updating storage metadata  135  and/or storing a persistent note on the non-volatile storage media  135 , as described above. Step  1320  may further comprise invalidating and/or removing other copies of the data on the non-volatile storage media, as described above. 
     The contextual format of the data on the storage medium  140  may be inconsistent with the modified logical interface. Therefore, steps  1330  and  1340  may comprise providing access to the data in the inconsistent contextual format through the modified logical interface and updating the contextual format of the data on the storage medium  140 , as described above. 
       FIG. 14  is a flow diagram of one embodiment of a range merge operation implemented by the storage layer  130  disclosed herein. Step  1410  may comprise cloning a set of LIDs within a logical address space  132 . Cloning the LIDs may comprise referencing the same set of data on the storage medium  140  (e.g., the same storage locations and/or storage addresses) through two or more different sets of LIDs. The two or more sets may include a working set of LIDs and an original, consistency set of LIDs. The working set of LIDs may be used to perform file modification operations, and the original, consistency set of LIDs may be configured to maintain an original, unmodified state of the data. 
     As disclosed above, the data cloned at step  1410  may be referenced by a set of LIDs, which may be bound to storage locations of the data on the storage medium  140 . Step  1410  may comprise allocating one or more other sets of LIDs within the logical address space  132  and/or within a separate address space. The one or more other sets of LIDs may comprise a logical capacity that is equivalent to the logical capacity of the original set of LIDs (e.g., include the same number of LIDs and/or correspond to the same amount of storage capacity). Step  1410  may further comprise associating and/or binding the logical identifiers of the one or more other sets of LIDs with the same data referenced by the original set of LIDs. Accordingly, step  1410  may comprise modifying the logical interface to the data to associate the data with a two or more different sets of LIDs. In some embodiments, step  1410  comprises allocating one or more sets of LIDs within the logical address space  132 , and binding the LIDs to the same set of storage addresses. Alternatively, or in addition, step  1410  may comprise creating one or more reference entries within a reference map  460  to indirectly link the LIDs of the two or more different sets of LIDs to the storage addresses through one or more reference entries, as disclosed in conjunction with  FIGS. 4A-E . Alternatively, step  1410  may be implemented by use of one or more intermediate mapping layers (e.g., as disclosed in conjunction with  FIGS. 5A-B ). Step  1410  may further comprise linking the two or more sets of LIDs through, inter alia, metadata  984  and/or  994  associated with the LIDs. The metadata  984  and/or  994  may be configured to indicate that the LID sets represent clones of the same storage entity (e.g., versions of the same file). The metadata  984  and/or  994  may be further configured to specify and/or reference a merge policy for the two or more sets of LIDs, as disclosed above. 
     Step  1410  may further comprise storing a persistent note  366  on the storage medium  140  configured to make the clone operation of step  1410  persistent and crash safe. The persistent note  366  may be configured to indicate the modified logical interface of the data (e.g., associate the data with the two or more sets of LIDs), indicate a merge policy of the clone operation, and the like. 
     Step  1420  may comprise performing storage operations within one or more of different LID ranges of step  1410 . The storage operations may be performed in response to requests received through the interface  131  from one or more storage clients  106 . The storage operations may comprise appending data to the storage medium  140 . The storage operations may, therefore, comprise modifying the associations and/or bindings between LIDs in one or more of LID sets and storage locations on the storage medium  140 . Modifying the associations and/or bindings may further comprise mapping LIDs in one or more of the LID sets to the appended data directly and/or through one or more indirect references and/or mapping layers. 
     Step  1430  may comprise merging the LID sets, as disclosed above. Merging LID sets may comprise incorporating modifications made in one of the LID ranges into one or more of the LID sets, as disclosed above. Step  1430  may further comprise resolving one or more merge conflicts in accordance with a merge policy. In some embodiments, merging comprises deleting (e.g., invalidating) one or more of the LID sets, which may comprise removing entries from the forward map  160 , removing shared references to storage locations from a reference count datastructure, removing reference entries from a reference map  460 , removing references in an intermediate mapping layer, and/or the like. Step  1430  may further comprise modifying a logical interface of the merged data, as disclosed above. The modified logical interface may update the LIDs used to reference data that was originally stored in reference to one or more of the LID sets. The modified logical interface may be inconsistent with the contextual format of the data on the storage medium  140 . Therefore, step  1430  may comprise appending one or more persistent notes  366  on the storage medium  140  to associate merged data with an updated logical interface of the data (e.g., associate data originally stored in association with LIDs in the second set with LIDs in the first set). Step  1430  may further comprise providing access to the data in the inconsistent contextual format and/or updating the contextual format of the data in one or more background operations, as disclosed above. 
       FIG. 15  is a flow diagram of another embodiment of a method  1500  for range merge operations. Step  1520  may comprise receiving a request to create a logical copy of a LID range. The request may be received from a storage client  106  through an interface  131  and/or may be part of a higher-level API provided by the storage layer  130 . The request may include an “operational mode” of the clone, which may include, but is not limited to, how the clones are to be synchronized, if at all; how merging is to occur (merge policy); whether the logical copy is to be designated as ephemeral; and so on. 
     Step  1530  may comprise allocating LIDs in the logical address space  132  to service the request. The allocation of step  1530  may further comprise reserving physical storage space to accommodate changes to the cloned LID range. The reservation of physical storage space may be predicated on the operational mode of the clone. For instance, if all changes are to be synchronized between the clone and the original address range, a small portion (if any) of physical storage space may be reserved. Alternatively, the storage layer  130  may reserve additional physical storage capacity for logical copy operations having a copy-on-conflict merge policy. Step  1530  may further comprise allocating the clone within a designated portion or segment of the logical address space  132  (e.g., a range dedicated for use with logical copy and/or clone operations). Accordingly, step  1530  may comprise allocating a second, different set of LIDs to clone a first set of LIDs. 
     Step  1540  may comprise updating the logical interface of data corresponding to the clone to reference both the original LIDs bound to the data as well as the cloned LIDs allocated at step  1530 . Step  1540  may comprise storing a persistent note  366  on the storage medium  140 , as disclosed above. 
     Step  1550  comprises receiving a storage request and determining if the storage request pertains to a LID in the first and/or second sets (cloned LID range). If so, the flow continues at step  1560 ; otherwise, the flow remains on step  1550 . 
     Step  1560  may comprise determining what (if any) operations are to be taken on the other associated LID ranges (e.g., synchronize allocation operations, etc.). The determination of step  1560  may comprise accessing metadata  984  and/or  994 , which may comprise and/or reference the synchronization policy of the clone. 
     Step  1570  may comprise performing the operations (if any) determined at step  1560  along with the requested storage operation. If one or more of the synchronization operations cannot be performed (e.g., additional logical address space  132  for one or more of the clones cannot be allocated), the underlying storage operation may fail. 
       FIG. 16  is a flow diagram of another embodiment of a method  1600  for implementing range clone and/or range merge operations. Step  1610  may comprise cloning a LID range, as disclosed above. Step  1610  may comprise cloning a set of LIDs associated with data stored on the storage medium  140  at respective storage addresses. Step  1610  may, therefore, comprise associating two or more different sets of LIDs with the same set of storage locations (e.g., the same data). Step  1610  may further comprise storing one or more persistent notes  366  on the storage medium  140  and/or rewriting the data in an updated contextual format, as disclosed above. Step  1610  may include linking the two or more sets of LIDs through, inter alia, metadata  984  and/or  994 . The metadata  984  and/or  994  may comprise and/or reference a clone synchronization policy, merge policy, and/or the like, as disclosed above. 
     Step  1620  may comprise performing storage operations in reference to one or more of the two or more cloned LID ranges. Step  1620  may comprise synchronizing allocation operations between the cloned ranges. The storage operations of step  1620  may comprise appending data to the storage medium  140  and/or associating the appended data with LIDs of one or more of the different LID ranges. 
     Step  1630  comprises receiving a request to merge the two or more LID ranges of step  1610 . The merge request may be received through the interface  131  and/or may be part of another, higher-level operation, such as an atomic storage operation or the like. 
     Step  1640  may comprise identifying merge conflicts between the two or more sets of LIDs (if any). Identifying merge conflicts may comprise identifying LIDs that were modified within more than one of the two or more cloned LID ranges. Referring back to  FIG. 9C , step  1640  may comprise identifying a merge conflict in state  941 D in response to determining that the LIDs  072 - 073  in range  914  were modified, as were the corresponding LIDs  972 - 973  in range  924 . As such, step  1640  may comprise comparing modifications within the LID clones to identify cases where conflicting modifications would map to the same LID in the merge operation. 
     Step  1650  may comprise resolving merge conflicts identified at step  1640 . Step  1650  may comprise determining an applicable merge policy, which, as disclosed above, may determine how merge conflicts are to be resolved. The merge policy may specify which version of a LID is included in the merged LID range and/or whether conflicts are resolved by maintaining separate copies of the LID ranges. Step  1650  may further comprise merging the LID ranges in accordance with the resolved merge conflicts, as disclosed above. 
       FIG. 17  is a flow diagram of one embodiment of a method  1700  for implementing atomic storage operations. Step  1710  may comprise accessing a second set of identifiers corresponding to a first set of identifiers of an atomic storage request. Step  1710  may be performed in response to an atomic storage request pertaining to the first set of identifiers (e.g., target LIDs, VIDs, or the like). The first set of identifiers may correspond to existing data stored on the storage medium  140 . Alternatively, the atomic storage request may comprise a request to allocate some (or all) of the first set of identifiers within the logical address space  132  or VAS  532 . The atomic storage request may correspond to a plurality of storage operations pertaining to different, disjoint vectors of LIDs and/or VIDs. Accordingly, the first set of identifiers may comprise a plurality of disjoint I/O vectors. 
     In some embodiments, step  1710  comprises allocating identifiers corresponding to the first set of identifiers in a separate address space, such as a transactional address space  1032 , intermediate index  1070 , VAS  532 , or the like. Alternatively, step  1710  may comprise allocating identifiers within a particular range or region of the logical address space  132 . Step  1710  may comprise allocating a corresponding set of identifiers of the same amount and/or logical capacity as the first set of identifiers. The second set of identifiers may be accessed and/or allocated by use of, inter alia, the redirection module  1034 , as disclosed herein. Step  1710  may further include linking the first and second sets of identifiers by use of, inter alia, a transaction map  1060 , as disclosed herein. 
     Step  1710  may further comprise implementing a range clone operation to bind the second set of identifiers to data of the first set of identifiers (if any). The range clone operation may be implemented using any of the embodiments disclosed herein, including, but not limited to, the range clone embodiments of  FIGS. 3A-E , the reference entry embodiments of  FIGS. 4A-E , and/or the intermediate mapping layer embodiments of  FIGS. 5A-B . 
     Step  1720  may comprise implementing storage operations of the atomic storage request in reference to the second set of identifiers accessed at step  1710 . Step  1720  may comprise redirecting storage operations from the first set of identifiers to the second set of identifiers (e.g., translating between the first and second sets of identifiers, as disclosed herein). The storage operations of step  1720  may comprise storing data on the storage medium  140  by use of, inter alia, the log storage module  137 . The storage operations of step  1720  may include, but are not limited to, a) operations to allocate storage resources (e.g., operations to allocate logical and/or physical storage resources), b) operations to deallocate storage resources (e.g., TRIM, persistent TRIM, and/or the like), c) writing data to the storage log, d) modifying existing data stored on the storage medium  140 , e) overwriting data stored on the storage medium  140 , and/or the like. The log storage module  136  may be configured to implement the storage operations out-of-place within the storage address space  144 , such that operations configured to modify, overwrite, and/or replace existing data stored on the storage medium  140  are appended to the storage log, while the data to be modified, overwritten, and/or replaced by the appended data remains unchanged on the storage medium  140 . 
     Data written to the storage medium  140  at step  1720  may comprise persistent metadata  114  configured to indicate the logical interface of the data. The persistent metadata  114  may be configured to bind the data to the second set of identifiers accessed at step  1710 . Alternatively, or in addition, the persistent metadata  114  may be configured to bind the appended data to identifiers of an intermediate address space, which are bound to the second set of identifiers through, inter alia, a persistent note  366  stored within the storage log. In some embodiments, the persistent metadata  114  may be further configured to indicate that the data is part of an atomic storage operation. Alternatively, or in addition, the data may be identified as part of an atomic storage operation by use of the persistent metadata  114  (e.g., through association between the data and the second set of identifiers). 
     Step  1730  may comprise completing the atomic storage request. Completion of the atomic storage request may comprise a range move operation configured to move the data of the storage operations implemented in step  1720  in reference to the second set of identifiers to the first set of target identifiers. The range move operation may be completed in a single, atomic write operation. The single atomic write operation may comprise an operation to store persistent metadata on the storage medium  140  (e.g., a persistent note  366  and/or  1066 B). The persistent metadata may be configured to modify the logical interface of the data written at step  1720  to bind the data to the first set of identifiers (e.g., the target LIDs or VIDs of the atomic storage request). The persistent metadata may be configured to modify the logical interface of a plurality of different storage vectors (e.g., a plurality of different, discontiguous sets of identifiers). Step  1730  may further comprise updating storage metadata  135  to reference the appended data through the first set of identifiers, which may comprise modifying one or more mappings in the forward index  160 , reference map  460 , intermediate mapping layer  1070 , and/or the like. 
     Step  1730  may further comprise rewriting the data stored at  1720  in a contextual format that is configured to associate the data with the first set of logical identifiers. The data may be rewritten in one or more background storage operations. The storage layer  130  and/or aggregation layer  530  may provide access to the data through the first set of identifiers before the data is rewritten. 
     Step  1730  may further comprise acknowledging completion of the atomic storage request. Completion may be acknowledged in response to storing the persistent metadata (persistent note  366  and/or  1066 B) on the storage medium  140  and/or determining that, within a reasonable certainty, the persistent metadata will be stored on the storage medium  140 . 
       FIG. 18  is a flow diagram of another embodiment of a method  1800  for atomic storage operations. Step  1810  may comprise receiving an atomic storage request. The atomic storage request may be received at the storage layer  130  through, inter alia, the storage interface  131 . Alternatively, the atomic storage request may be received through the interface  531  of the aggregation layer  530 . The atomic storage request may comprise a plurality of atomic storage operations to be performed within respective I/O vectors, each of which may correspond to a different, respective target set of LIDs and/or VIDs. 
     Step  1820  may comprise implementing the storage operations of the atomic storage request in reference to a set of transactional or in-process identifiers. The transactional identifiers may correspond to a particular region of the logical address space  132 ; a VAS  532  (or region within a particular VAS  532 ); a separate namespace, such as the transactional address space  1032  disclosed above; and/or the like. Step  1820  may comprise allocating and/or identifying transactional identifiers corresponding to the target identifiers of the atomic storage request; the transactional identifiers may comprise a plurality of identifier ranges and/or extents corresponding to the I/O vectors of a vectored atomic storage request. In some embodiments, the transactional identifiers may be allocated and/or identified in different ranges and/or extents than the target identifiers. For example, the transactional identifiers used to implement an atomic storage operation corresponding to two discontiguous ranges of LIDs  1024 - 2048  and  6144 - 7186  may be implemented within a single range of ephemeral identifiers  10240 - 12288  or a plurality of smaller ranges and/or extents of transactional identifiers. The transactional identifiers may be linked to the target identifiers by use of, inter alia, storage metadata  135 . In some embodiments, the transactional identifiers are linked to the target identifiers in a transaction map  1060 . The transaction map  1060  may be further configured to bind the transactional identifiers to storage locations corresponding to the target LIDs and/or VIDs. 
     Step  1820  may further comprise implementing storage operations of the atomic storage request in reference to the transactional identifiers. One or more of the atomic storage operations may be predicated on the availability of resources within a target or destination namespace, such as the logical address space  132 , VAS  532 , or the like. In some embodiments, for example, the atomic storage request may comprise a request to allocate a particular set of LIDs. Step  1820  may, therefore, comprise provisionally reserving logical capacity within a target namespace by use of, inter alia, one or more persistent notes  366 , as disclosed above. Step  1820  may further comprise allocating and/or reserving corresponding transactional identifiers, as disclosed above. In response to a failure of the allocation operation, the atomic storage module  1035  may: a) fail the atomic storage request or b) allocate and/or reserve a different set of target LIDs within the target namespace, which may be returned upon completion of the atomic storage operation. 
     The storage operations of step  1820  may further comprise appending data to the storage log in association with persistent metadata  114  that is configured to identify the data as being part of an atomic storage operation. The persistent metadata may comprise the transactional identifiers of step  1810 . Alternatively, or in addition, the persistent metadata may comprise an atomic storage flag (or other datum) configured to indicate that the data is part of an incomplete atomic storage operation. 
     Step  1830  may comprise completing the atomic storage request. Step  1830  may comprise closing the atomic storage request implemented at step  1820 . Closing the atomic storage request may comprise performing a range move operation to bind the data of the storage operations of step  1820  to the target identifiers, which may comprise updating storage metadata  135  to map the target identifiers to the data stored in the storage operations of step  1820 . The range move operation may further comprise implementing one or more TRIM operations within the target namespace, as disclosed above. Completing the atomic storage request may further comprise storing persistent metadata on the storage medium  140  that is configured to: a) bind data of the atomic storage request to the target identifiers and/or b) indicate that the atomic storage request has been completed. The persistent metadata may be appended to the storage log in a single storage operation (e.g., in a persistent note  366  and/or  1066 B). Step  1830  may further comprise acknowledging completion of the atomic storage request. Completion may be acknowledged in response to completing the range move operations and/or storing the corresponding persistent metadata. 
       FIG. 19  is a flow diagram of another embodiment of a method  1900  for atomic storage operations. Step  1910  may comprise accessing the storage log on the storage medium  140 . Step  1910  may be performed by the reconstruction module  1037  to reconstruct the storage metadata  135  following a failure condition. The reconstruction module  1037  may be configured to access the storage log according to the log order of the storage log. The reconstruction module  1037  may be configured to identify the last append point within the storage log, and traverse the storage log in a reverse log order (e.g., from the head of the log toward the tail). 
     Step  1920  may comprise identifying data of an incomplete atomic storage request. Step  1920  may comprise identifying data that is bound to transactional or in-process identifiers and/or identifiers of a transactional and/or in-process address space  1032 . Step  1920  may comprise accessing persistent metadata  114  stored with data segments in the storage log. Step  1920  may further comprise determining that other persistent metadata within the storage log fails to modify the identified data bindings (e.g., does not associate the data segments with identifiers in a different address space, such as the logical address space  132  and/or VAS  532 ). 
     Step  1930  may comprise omitting the identified data segments from the storage metadata  135 , which may comprise invalidating the storage location(s) comprising the data, and omitting entries corresponding to the data segments from the forward map  160 , intermediate mapping layer  1070 , and/or the like. Step  1930  may, therefore, comprise rolling back a failed atomic storage operation, such that data of the partially completed atomic storage operation does not affect the target identifiers and/or namespace. 
     This disclosure has been made with reference to various exemplary embodiments. However, those skilled in the art will recognize that changes and modifications may be made to the exemplary embodiments without departing from the scope of the present disclosure. For example, various operational steps, as well as components for carrying out operational steps, may be implemented in alternative ways depending upon the particular application or in consideration of any number of cost functions associated with the operation of the system (e.g., one or more of the steps may be deleted, modified, or combined with other steps). Therefore, this disclosure is to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope thereof. Likewise, benefits, other advantages, and solutions to problems have been described above with regard to various embodiments. However, benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, a required, or an essential feature or element. As used herein, the terms “comprises,” “comprising,” and any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, a method, an article, or an apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, system, article, or apparatus. Also, as used herein, the terms “coupled,” “coupling,” and any other variation thereof are intended to cover a physical connection, an electrical connection, a magnetic connection, an optical connection, a communicative connection, a functional connection, and/or any other connection. 
     Additionally, as will be appreciated by one of ordinary skill in the art, principles of the present disclosure may be reflected in a computer program product on a machine-readable storage medium having machine-readable program code means embodied in the storage medium. Any tangible, non-transitory machine-readable storage medium may be utilized, including magnetic storage devices (hard disks, floppy disks, and the like), optical storage devices (CD-ROMs, DVDs, Blu-ray discs, and the like), flash memory, and/or the like. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions that execute on the computer or other programmable data processing apparatus create means for implementing the functions specified. These computer program instructions may also be stored in a machine-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the machine-readable memory produce an article of manufacture, including implementing means that implement the function specified. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified. 
     While the principles of this disclosure have been shown in various embodiments, many modifications of structure, arrangements, proportions, elements, materials, and components that are particularly adapted for a specific environment and operating requirements may be used without departing from the principles and scope of this disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure.