Patent Publication Number: US-11392551-B2

Title: Storage system utilizing content-based and address-based mappings for deduplicatable and non-deduplicatable types of data

Description:
FIELD 
     The field relates generally to information processing systems, and more particularly to storage in information processing systems. 
     BACKGROUND 
     Various types of content addressable storage systems are known. Some content addressable storage systems allow data pages of one or more logical storage volumes to be accessed using content-based signatures that are computed from content of respective ones of the data pages. Such content addressable storage system arrangements facilitate implementation of deduplication and compression. For example, the storage system need only maintain a single copy of a given data page even though that same data page may be part of multiple logical storage volumes. Although these and other content addressable storage systems typically provide a high level of storage efficiency through deduplication and compression, some inefficiencies may arise in cases where the data is not easily deduplicated. 
     SUMMARY 
     Illustrative embodiments provide storage systems that are configured for determining a deduplication type of target data and storing the target data utilizing content-based or address-based mappings depending on the deduplication type. 
     In an illustrative embodiment, an apparatus is disclosed. The apparatus comprises a storage system comprising a plurality of storage devices and a storage controller. The storage controller is configured to receive information indicating whether target data is one of a non-deduplicatable type of data and a deduplicatable type of data. Responsive to the information indicating that the target data is of the deduplicatable type, the storage controller is configured to utilize a content-based mapping generated based on a content of the target data to identify a corresponding physical address for storing the target data. Responsive to the information indicating that the target data is of the non-deduplicatable type, the storage controller is configured to utilize an address-based mapping generated based on a logical address associated with the target data to identify a corresponding physical address for storing the target data. The storage controller is implemented by at least one processing device comprising a processor coupled to a memory. 
     In some embodiments, responsive to the information indicating that the target data is of the deduplicatable type, the storage controller is further configured to store the target data on the plurality of storage devices based on the identified physical address corresponding to the content-based mapping. Responsive to the information indicating that the target data is of the non-deduplicatable type, the storage controller is further configured to store the target data on the plurality of storage devices based on the identified physical address corresponding to the address-based mapping. In further embodiments, the target data is stored on the plurality of storage devices at the physical address corresponding to the content-based mapping prior to receiving the information, wherein the storing of the target data on the plurality of storage devices based on the identified physical address corresponding to the address-based mapping responsive to the information indicating that the target data is of the non-deduplicatable type comprises moving the target data from the physical address corresponding to the content-based mapping to the physical address corresponding to the address-based mapping. 
     In other embodiments, the information is received from a driver implemented on a host device. The driver is configured to determine whether the target data is of the deduplicatable type or the non-deduplicatable type, to generate the information based on the determination of whether the target data is of the deduplicatable type or the non-deduplicatable type and to provide the information to the storage controller. 
     In some further embodiments, determining whether the target data is of the deduplicatable type or the non-deduplicatable type comprises identifying which virtual machines (VMs) of the host device comprise data of the non-deduplicatable type, identifying mappings of the identified virtual machines to corresponding logical volumes of the storage system, obtaining snapshots of the corresponding logical volumes, parsing the snapshots to determine which blocks within the logical volumes comprise data of the non-deduplicatable type and determining whether or not the target data is included in the blocks determined to comprise data of the non-deduplicatable type. Responsive to determining that the target data is included in the blocks determined to comprise data of the non-deduplicatable type, determining whether the target data is of the deduplicatable type or the non-deduplicatable type further comprises determining that the target data is of the non-deduplicatable type. Responsive to determining that the target data is not included in the blocks determined to comprise data of the non-deduplicatable type, determining whether the target data is of the deduplicatable type or the non-deduplicatable type further comprises determining that the target data is of the deduplicatable type. 
     In yet other further embodiments, determining whether the target data is of the deduplicatable type or the non-deduplicatable type comprises identifying which files of the host device comprise a data structure comprising data of the non-deduplicatable type, identifying mappings of the identified files to corresponding logical volumes of the storage system, parsing blocks within the logical volumes to determine which blocks comprise data corresponding to the data structures comprising the data of the non-deduplicatable type and determining whether or not the target data is included in the blocks determined to comprise the data corresponding to the data structures comprising the data of the non-deduplicatable type. Responsive to determining that the target data is included in the blocks determined to comprise the data corresponding to the data structures comprising the data of the non-deduplicatable type, determining whether the target data is of the deduplicatable type or the non-deduplicatable type further comprises determining that the target data is of the non-deduplicatable type. Responsive to determining that the target data is not included in the blocks determined to comprise data corresponding to the data structures comprising the data of the non-deduplicatable type, determining whether the target data is of the deduplicatable type or the non-deduplicatable type further comprises determining that the target data is of the deduplicatable type. 
     In some embodiments, the driver is configured to intercept an input-output request associated with the target data. In such embodiments, generating the information based on the determination of whether the target data is of the deduplicatable type or the non-deduplicatable type comprises setting a portion of the intercepted input-output request to a value corresponding to the determined type of the target data. The value of the portion is configured to indicate to the storage controller the determined type of the target data. In such embodiments, providing the information to the storage controller comprises providing the intercepted input-output request with the set portion. 
     These and other illustrative embodiments include, without limitation, apparatus, systems, methods and processor-readable storage media. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an information processing system comprising a content addressable storage system configured for utilizing both content-based and address-based mapping between logical addresses and physical addresses in an illustrative embodiment. 
         FIG. 2  illustrates a portion of a distributed storage controller of a content addressable storage system showing one possible arrangement utilizing control modules and data modules interconnected by a mesh network and configured for utilizing both content-based and address-based mapping between logical addresses and physical addresses in an illustrative embodiment. 
         FIGS. 3A and 3B  show examples of internal hash metadata structures in an illustrative embodiment. 
         FIG. 4  illustrates a block diagram of an example information processing system in an illustrative embodiment. 
         FIG. 5  is a flow diagram showing a process for utilizing both content-based and address-based mapping between logical addresses and physical addresses in an illustrative embodiment. 
         FIG. 6  is a flow diagram showing a process for generating information indicating a type of target data in an illustrative embodiment. 
         FIG. 7  is a flow diagram showing a process for utilizing both content-based and address-based mapping between logical addresses and physical addresses based on the generated information of  FIG. 6  in an illustrative embodiment. 
         FIGS. 8 and 9  show examples of processing platforms that may be utilized to implement at least a portion of an information processing system in illustrative embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative embodiments will be described herein with reference to exemplary information processing systems and associated computers, servers, storage devices and other processing devices. It is to be appreciated, however, that these and other embodiments are not restricted to the particular illustrative system and device configurations shown. Accordingly, the term “information processing system” as used herein is intended to be broadly construed, so as to encompass, for example, processing systems comprising cloud computing and storage systems, as well as other types of processing systems comprising various combinations of physical and virtual processing resources. An information processing system may therefore comprise, for example, at least one data center or other cloud-based system that includes one or more clouds hosting multiple tenants that share cloud resources. Numerous other types of enterprise computing and storage systems are also encompassed by the term “information processing system” as that term is broadly used herein. 
       FIG. 1  shows an information processing system  100  configured in accordance with an illustrative embodiment. The information processing system  100  comprises a computer system  101  that includes host devices  102 - 1 ,  102 - 2 , . . .  102 -N. The host devices  102  communicate over a network  104  with a content addressable storage system  105 . The content addressable storage system  105  is an example of what is more generally referred to herein as a “storage system,” and it is to be appreciated that a wide variety of other types of storage systems can be used in other embodiments. In illustrative embodiments, the content addressable storage system  105  utilizes both content-based mapping and address-based mapping of logical addresses to physical addresses. 
     The host devices  102  and content addressable storage system  105  illustratively comprise respective processing devices of one or more processing platforms. For example, the host devices  102  and the content addressable storage system  105  can each comprise one or more processing devices each having a processor and a memory, possibly implementing virtual machines and/or containers, although numerous other configurations are possible. 
     The host devices  102  and content addressable storage system  105  may be part of an enterprise computing and storage system, a cloud-based system or another type of system. For example, the host devices  102  and the content addressable storage system  105  can be part of cloud infrastructure such as an Amazon Web Services (AWS) system. Other examples of cloud-based systems that can be used to provide one or more of host devices  102  and content addressable storage system  105  include Google Cloud Platform (GCP) and Microsoft Azure. 
     The host devices  102  are configured to write data to and read data from the content addressable storage system  105 . The host devices  102  and the content addressable storage system  105  may be implemented on a common processing platform, or on separate processing platforms. A wide variety of other types of host devices can be used in other embodiments. 
     The host devices  102  in some embodiments illustratively provide compute services such as execution of one or more applications on behalf of each of one or more users associated with respective ones of the host devices  102 . 
     The term “user” herein is intended to be broadly construed so as to encompass numerous arrangements of human, hardware, software or firmware entities, as well as combinations of such entities. Compute and/or storage services may be provided for users under a platform-as-a-service (PaaS) model, an infrastructure-as-a-service (IaaS) model and/or a function-as-a-service (FaaS) model, although it is to be appreciated that numerous other cloud infrastructure arrangements could be used. Also, illustrative embodiments can be implemented outside of the cloud infrastructure context, as in the case of a stand-alone computing and storage system implemented within a given enterprise. 
     The network  104  is assumed to comprise a portion of a global computer network such as the Internet, although other types of networks can be part of the network  104 , including a wide area network (WAN), a local area network (LAN), a satellite network, a telephone or cable network, a cellular network, a wireless network such as a WiFi or WiMAX network, or various portions or combinations of these and other types of networks. The network  104  in some embodiments therefore comprises combinations of multiple different types of networks each comprising processing devices configured to communicate using Internet Protocol (IP) or other communication protocols. 
     As a more particular example, some embodiments may utilize one or more high-speed local networks in which associated processing devices communicate with one another utilizing Peripheral Component Interconnect express (PCIe) cards of those devices, and networking protocols such as InfiniB and, Gigabit Ethernet or Fibre Channel. Numerous alternative networking arrangements are possible in a given embodiment, as will be appreciated by those skilled in the art. 
     The content addressable storage system  105  is accessible to the host devices  102  over the network  104 . The content addressable storage system  105  comprises a plurality of storage devices  106  and an associated storage controller  108 . The storage devices  106  illustratively store metadata pages  110  and user data pages  112 . The user data pages  112  in some embodiments are organized into sets of logical units (LUNs) each accessible to one or more of the host devices  102 . The LUNs may be viewed as examples of what are also referred to herein as logical storage volumes of the content addressable storage system  105 . 
     In some embodiments, the storage devices  106  may implement at least one redundant array of independent disks (RAID) 6 arrangement involving multiple ones of the storage devices  106 . Additional or alternative RAID or non-RAID arrangements can be used to store data in the storage system  105 . 
     The RAID 6 arrangement in this embodiment illustratively includes an array of different “disks,” each a different physical storage device of the storage devices  106 . Multiple such physical storage devices are typically utilized to store data of a given LUN or other logical storage volume in the storage system  105 . For example, data pages or other data blocks of a given LUN or other logical storage volume can be “striped” along with its corresponding parity information across multiple ones of the disks in the RAID 6 arrangement. 
     A given RAID 6 arrangement in an illustrative embodiment defines block-level striping with double distributed parity and provides fault tolerance of two drive failures, so that the array continues to operate with up to two failed drives, irrespective of which two drives fail. In the RAID 6 arrangement, data blocks and corresponding p-type and q-type parity information are arranged in a row or stripe. Other data and parity blocks in the RAID 6 arrangement are distributed over the disks in a similar manner, collectively providing a diagonal-based configuration for the p-type and q-type parity information. Other types of RAID implementations can be used, as will be appreciated by those skilled in the art, possibly using error correcting codes in place of parity information. 
     Additional details regarding exemplary techniques for storing data in RAID arrays such as a RAID 6 arrangement are disclosed in U.S. Pat. No. 9,552,258, entitled “Method and System for Storing Data in RAID Memory Devices,” which is incorporated by reference herein. 
     The storage devices  106  illustratively comprise solid state drives (SSDs). Such SSDs are implemented using non-volatile memory (NVM) devices such as flash memory. Other types of NVM devices that can be used to implement at least a portion of the storage devices  106  include non-volatile random access memory (NVRAM), phase-change RAM (PC-RAM) and magnetic RAM (MRAM). These and various combinations of multiple different types of NVM devices may also be used. 
     However, it is to be appreciated that other types of storage devices can be used in other embodiments. For example, a given storage system as the term is broadly used herein can include a combination of different types of storage devices, as in the case of a multi-tier storage system comprising a flash-based fast tier and a disk-based capacity tier. In such an embodiment, each of the fast tier and the capacity tier of the multi-tier storage system comprises a plurality of storage devices with different types of storage devices being used in different ones of the storage tiers. For example, the fast tier may comprise flash drives while the capacity tier comprises hard disk drives. The particular storage devices used in a given storage tier may be varied in other embodiments, and multiple distinct storage device types may be used within a single storage tier. The term “storage device” as used herein is intended to be broadly construed, so as to encompass, for example, flash drives, solid state drives, hard disk drives, hybrid drives or other types of storage devices. 
     In some embodiments, the content addressable storage system  105  illustratively comprises a scale-out all-flash content addressable storage array such as an XtremIO™ storage array from Dell EMC of Hopkinton, Mass. For example, the content addressable storage system  105  can comprise an otherwise conventional XtremIO™ storage array or other type of content addressable storage system that is suitably modified to incorporate address mapping logic as disclosed herein. Other types of storage arrays, including by way of example VNX® and Symmetrix VMAXx storage arrays also from Dell EMC, can be used to implement content addressable storage system  105  in other embodiments. 
     The term “storage system” as used herein is therefore intended to be broadly construed, and should not be viewed as being limited to content addressable storage systems or flash-based storage systems. A given storage system as the term is broadly used herein can comprise, for example, network-attached storage (NAS), storage area networks (SANs), direct-attached storage (DAS) and distributed DAS, as well as combinations of these and other storage types, including software-defined storage. 
     Other particular types of storage products that can be used in implementing content addressable storage system  105  in illustrative embodiments include all-flash and hybrid flash storage arrays such as Unity™, software-defined storage products such as ScaleIO™ and ViPR®, cloud storage products such as Elastic Cloud Storage (ECS), object-based storage products such as Atmos®, and scale-out NAS clusters comprising Isilon® platform nodes and associated accelerators, all from Dell EMC. Combinations of multiple ones of these and other storage products can also be used in implementing a given storage system in an illustrative embodiment. 
     The content addressable storage system  105  in the  FIG. 1  embodiment is implemented as at least a portion of a clustered storage system and includes a plurality of storage nodes  115  each comprising a corresponding subset of the storage devices  106 . Other clustered storage system arrangements comprising multiple storage nodes can be used in other embodiments. A given clustered storage system may include not only storage nodes  115  but also additional storage nodes  120  coupled to network  104 . Alternatively, such additional storage nodes  120  may be part of another clustered storage system of the system  100 . Each of the storage nodes  115  of the content addressable storage system  105  is assumed to be implemented using at least one processing device comprising a processor coupled to a memory. 
     Other arrangements of storage nodes or other types of nodes can be used. The term “node” as used herein is intended to be broadly construed and a given such node need not include storage devices. 
     The storage controller  108  in this embodiment is implemented in a distributed manner so as to comprise a plurality of distributed storage controller components implemented on respective ones of the storage nodes  115 . The storage controller  108  is therefore an example of what is more generally referred to herein as a “distributed storage controller.” Accordingly, in subsequent description herein, the storage controller  108  is more particularly referred to as a distributed storage controller. Other types of potentially non-distributed storage controllers can be used in other embodiments. 
     Each of the storage nodes  115  in this embodiment further comprises a set of processing modules configured to communicate over one or more networks with corresponding sets of processing modules on other ones of the storage nodes  115 . The sets of processing modules of the storage nodes  115  collectively comprise at least a portion of the distributed storage controller  108  of the content addressable storage system  105 . 
     The modules of the distributed storage controller  108  in the present embodiment more particularly comprise different sets of processing modules implemented on each of the storage nodes  115 . The set of processing modules of each of the storage nodes  115  comprises at least a control module  108 C, a data module  108 D and a routing module  108 R. The distributed storage controller  108  further comprises one or more management (MGMT) modules  108 M. For example, only a single one of the storage nodes  115  may include a management module  108 M. It is also possible that management modules  108 M may be implemented on each of at least a subset of the storage nodes  115 . 
     Each of the storage nodes  115  of the content addressable storage system  105  therefore comprises a set of processing modules configured to communicate over one or more networks with corresponding sets of processing modules on other ones of the storage nodes. A given such set of processing modules implemented on a particular storage node illustratively includes at least one control module  108 C, at least one data module  108 D and at least one routing module  108 R, and possibly a management module  108 M. These sets of processing modules of the storage nodes collectively comprise at least a portion of the distributed storage controller  108 . 
     Communication links may be established between the various processing modules of the distributed storage controller  108  using well-known communication protocols such as IP, Transmission Control Protocol (TCP), and remote direct memory access (RDMA). For example, respective sets of IP links used in data transfer and corresponding messaging could be associated with respective different ones of the routing modules  108 R. 
     It is assumed in some embodiments that the processing modules of the distributed storage controller  108  are interconnected in a full mesh network, such that a process of one of the processing modules can communicate with processes of any of the other processing modules. Commands issued by the processes can include, for example, remote procedure calls (RPCs) directed to other ones of the processes. 
     The distributed storage controller  108  of the content addressable storage system  105  in the present embodiment is configured to control the implementation of functionality for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings as disclosed herein. The distributed storage controller  108  is assumed to comprise a type of “processing device” as that term is broadly used herein, and more particularly comprises at least one processor coupled to a memory. 
     Various aspects of page storage in the content addressable storage system  105  will now be described in greater detail. As indicated above, the storage devices  106  are configured to store metadata pages  110  and user data pages  112 , and in some embodiments may also store additional information not explicitly shown such as checkpoints and write journals. The metadata pages  110  and the user data pages  112  are illustratively stored in respective designated metadata and user data areas of the storage devices  106 . Accordingly, metadata pages  110  and user data pages  112  may be viewed as corresponding to respective designated metadata and user data areas of the storage devices  106 . 
     The term “page” as used herein is intended to be broadly construed so as to encompass any of a wide variety of different types of blocks that may be utilized in a block storage device of a storage system. Such storage systems are not limited to content addressable storage systems of the type disclosed in some embodiments herein, but are more generally applicable to any storage system that includes one or more block storage devices. Different native page sizes are generally utilized in different storage systems of different types. For example, XtremIO™ X1 storage arrays utilize a native page size of 8 KB, while XtremIO™ X2 storage arrays utilize a native page size of 16 KB. Larger native page sizes of 64 KB and 128 KB are utilized in VMAX® V2 and VMAX® V3 storage arrays, respectively. The native page size generally refers to a typical page size at which the storage system ordinarily operates, although it is possible that some storage systems may support multiple distinct page sizes as a configurable parameter of the system. Each such page size of a given storage system may be considered a “native page size” of the storage system as that term is broadly used herein. 
     A given “page” as the term is broadly used herein should therefore not be viewed as being limited to any particular range of fixed sizes. In some embodiments, a page size of 8 KB is used, but this is by way of example only and can be varied in other embodiments. For example, page sizes of 4 KB, 16 KB or other values can be used. Accordingly, illustrative embodiments can utilize any of a wide variety of alternative paging arrangements for organizing the metadata pages  110  and the user data pages  112 . 
     The user data pages  112  are part of a plurality of LUNs configured to store files, blocks, objects or other arrangements of data, each also generally referred to herein as a “data item,” on behalf of users associated with host devices  102 . Each such LUN may comprise particular ones of the above-noted pages of the user data area. The user data stored in the user data pages  112  can include any type of user data that may be utilized in the system  100 . The term “user data” herein is therefore also intended to be broadly construed. 
     The content addressable storage system  105  is configured to generate hash metadata providing a mapping between content-based digests of respective ones of the user data pages  112  and corresponding physical locations of those pages in the user data area. Content-based digests generated using hash functions are also referred to herein as “hash digests.” Such hash digests or other types of content-based digests are examples of what are more generally referred to herein as “content-based signatures” of the respective user data pages  112 . 
     In illustrative embodiments, the content addressable storage system  105  is also configured to generate hash metadata providing a mapping between logical addresses and corresponding physical locations in the user data area that are not content-based. For example, the hash metadata may be based on hashes of the logical block addresses themselves. 
     The hash metadata generated by the content addressable storage system  105 , whether content-based or address-based, is illustratively stored as metadata pages  110  in the metadata area. The generation and storage of the hash metadata is assumed to be performed under the control of the distributed storage controller  108 . 
     Each of the metadata pages  110  characterizes a plurality of the user data pages  112 . For example, a given set of user data pages representing a portion of the user data pages  112  illustratively comprises a plurality of user data pages denoted User Data Page 1, User Data Page 2, . . . User Data Page n. 
     Each of the user data pages  112  in this example is characterized by a LUN identifier, an offset and a hash value. The hash value is either a content-based signature generated as a hash function of content of the corresponding user data page or an address-based hash of a logical address. Illustrative hash functions that may be used to generate the content-based signature or address-based hash include the SHA1 hash function, where SHA denotes Secure Hashing Algorithm, or other secure hashing algorithms known to those skilled in the art, including SHA2, SHA256 and many others. The content-based signatures and address-based hashes are utilized to determine the location of the corresponding user data page within the user data area of the storage devices  106 . 
     Each of the metadata pages  110  in the present embodiment is assumed to have a signature that is not content-based. For example, the metadata page signatures may be generated using hash functions or other signature generation algorithms that do not utilize content of the metadata pages as input to the signature generation algorithm. Also, each of the metadata pages is assumed to characterize a different set of the user data pages. 
     A given set of metadata pages representing a portion of the metadata pages  110  in an illustrative embodiment comprises metadata pages denoted Metadata Page 1, Metadata Page 2, . . . Metadata Page m, having respective signatures denoted Signature 1, Signature 2, . . . Signature m. Each such metadata page characterizes a different set of n user data pages. For example, the characterizing information in each metadata page can include the LUN identifiers, offsets and hash values for each of the n user data pages that are characterized by that metadata page. It is to be appreciated, however, that the user data and metadata page configurations described above are examples only, and numerous alternative user data and metadata page configurations can be used in other embodiments. 
     Ownership of a user data logical address space within the content addressable storage system  105  is illustratively distributed among the control modules  108 C. 
     The functionality for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings in this embodiment is assumed to be distributed across multiple distributed processing modules, including at least a subset of the processing modules  108 C,  108 D,  108 R and  108 M of the distributed storage controller  108 . 
     For example, the management module  108 M of the distributed storage controller  108  may include mapping logic that engages or otherwise interacts with corresponding control logic instances in at least a subset of the control modules  108 C, data modules  108 D and routing modules  108 R in order to implement content-based and address-based mapping of logical addresses to physical addresses. 
     In some embodiments, the content addressable storage system  105  comprises an XtremIO™ storage array suitably modified to incorporate techniques for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings as disclosed herein. 
     In arrangements of this type, the control modules  108 C, data modules  108 D and routing modules  108 R of the distributed storage controller  108  illustratively comprise respective C-modules, D-modules and R-modules of the XtremIO™ storage array. The one or more management modules  108 M of the distributed storage controller  108  in such arrangements illustratively comprise a system-wide management module (SYM module) of the XtremIO™ storage array, although other types and arrangements of system-wide management modules can be used in other embodiments. Accordingly, functionality for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings in some embodiments is implemented under the control of at least one system-wide management module of the distributed storage controller  108 , utilizing the C-modules, D-modules and R-modules of the XtremIO™ storage array. 
     In the above-described XtremIO™ storage array example, each user data page has a fixed size such as 8 KB and its content-based signature is a 20-byte signature generated using an SHA1 hash function. Also, each page has a LUN identifier and an offset, and so is characterized by &lt;lun_id, offset, signature&gt;. 
     The content-based signature in the present example comprises a content-based digest of the corresponding data page. Such a content-based digest is more particularly referred to as a “hash digest” of the corresponding data page, as the content-based signature is illustratively generated by applying a hash function such as SHA1 to the content of that data page. The full hash digest of a given data page is given by the above-noted 20-byte signature. The hash digest may be represented by a corresponding “hash handle,” which in some cases may comprise a particular portion of the hash digest. The hash handle illustratively maps on a one-to-one basis to the corresponding full hash digest within a designated cluster boundary or other specified storage resource boundary of a given storage system. In arrangements of this type, the hash handle provides a lightweight mechanism for uniquely identifying the corresponding full hash digest and its associated data page within the specified storage resource boundary. The hash digest and hash handle are both considered examples of “content-based signatures” as that term is broadly used herein. 
     Examples of techniques for generating and processing hash handles for respective hash digests of respective data pages are disclosed in U.S. Pat. No. 9,208,162, entitled “Generating a Short Hash Handle,” and U.S. Pat. No. 9,286,003, entitled “Method and Apparatus for Creating a Short Hash Handle Highly Correlated with a Globally-Unique Hash Signature,” both of which are incorporated by reference herein. 
     As mentioned previously, storage controller components in an XtremIO™ storage array illustratively include C-module, D-module and R-module components. For example, separate instances of such components can be associated with each of a plurality of storage nodes in a clustered storage system implementation. 
     The distributed storage controller  108  in this example is configured to group consecutive pages into page groups, to arrange the page groups into slices, and to assign the slices to different ones of the C-modules. For example, if there are 1024 slices distributed evenly across the C-modules, and there are a total of 16 C-modules in a given implementation, each of the C-modules “owns” 1024/16=64 slices. In such arrangements, different ones of the slices are assigned to different ones of the control modules  108 C such that control of the slices within the distributed storage controller  108  is substantially evenly distributed over the control modules  108 C of the distributed storage controller  108 . 
     The D-module allows a user to locate a given user data page based on its signature. Each metadata page also has a size of 8 KB and includes multiple instances of the &lt;lun_id, offset, signature&gt; for respective ones of a plurality of the user data pages. Such metadata pages are illustratively generated by the C-module but are accessed using the D-module based on a metadata page signature. 
     The metadata page signature in this embodiment is a 20-byte signature but is not based on the content of the metadata page. Instead, the metadata page signature is generated based on an 8-byte metadata page identifier that is a function of the LUN identifier and offset information of that metadata page. 
     If a user wants to read a user data page having a particular LUN identifier and offset, the corresponding metadata page identifier is first determined, then the metadata page signature is computed for the identified metadata page, and then the metadata page is read using the computed signature. In this embodiment, the metadata page signature is more particularly computed using a signature generation algorithm that generates the signature to include a hash of the 8-byte metadata page identifier, one or more ASCII codes for particular predetermined characters, as well as possible additional fields. The last bit of the metadata page signature may always be set to a particular logic value so as to distinguish it from the user data page signature in which the last bit may always be set to the opposite logic value. 
     The metadata page signature is used to retrieve the metadata page via the D-module. This metadata page will include the &lt;lun_id, offset, signature&gt; for the user data page if the user page exists. The signature of the user data page is then used to retrieve that user data page, also via the D-module. 
     Write requests processed in the content addressable storage system  105  each illustratively comprise one or more IO operations directing that at least one data item of the content addressable storage system  105  be written to in a particular manner. A given write request is illustratively received in the content addressable storage system  105  from a host device, illustratively one of the host devices  102 . In some embodiments, a write request is received in the distributed storage controller  108  of the content addressable storage system  105 , and directed from one processing module to another processing module of the distributed storage controller  108 . For example, a received write request may be directed from a routing module  108 R of the distributed storage controller  108  to a particular control module  108 C of the distributed storage controller  108 . Other arrangements for receiving and processing write requests from one or more host devices can be used. 
     The term “write request” as used herein is intended to be broadly construed, so as to encompass one or more IO operations directing that at least one data item of a storage system be written to in a particular manner. A given write request is illustratively received in a storage system from a host device. 
     In the XtremIO™ context, the C-modules, D-modules and R-modules of the storage nodes  115  communicate with one another over a high-speed internal network such as an InfiniBand network. The C-modules, D-modules and R-modules coordinate with one another to accomplish various IO processing tasks. 
     The write requests from the host devices  102  identify particular data pages to be written in the content addressable storage system  105  by their corresponding logical addresses each comprising a LUN ID and an offset. 
     As noted above, a given one of the content-based signatures illustratively comprises a hash digest of the corresponding data page, with the hash digest being generated by applying a hash function to the content of that data page. The hash digest may be uniquely represented within a given storage resource boundary by a corresponding hash handle. 
     The content addressable storage system  105  utilizes a two-level mapping process to map logical block addresses to physical addresses. The first level of mapping uses an address-to-hash (A2H) table and the second level of mapping uses a hash metadata (HMD) table, with the A2H and HMD tables corresponding to respective logical and physical layers of the content-based and address-based signature mapping within the content addressable storage system  105 . The HMD table or a given portion thereof in some embodiments disclosed herein is more particularly referred to as a hash-to-data (H2D) table. 
     The first level of mapping using the A2H table associates logical addresses with respective hash values. For example, content-based mapping may associate logical addresses of respective data pages with respective content-based signatures of those data pages. Address-based mapping may associate logical addresses with respective hashes of those logical addresses. This is also referred to as logical layer mapping. An example of an A2H table according to an embodiment of the present disclosure is illustrated in  FIG. 3A . As seen in  FIG. 3A , for example, each entry in the A2H table  300  includes a logical block address  302 , a CAS/LBA flag  304  (where CAS stands for content addressable storage and LBA stands for logical block address), and the hash value  306 , e.g., a content-based signature or hash handle or a hash of the logical block address  302 . In some embodiments, the logical block address  302  may be used as a key for accessing the entries in the table. 
     In illustrative embodiments, the CAS/LBA flag  304  may be utilized by content addressable storage system  105  to indicate whether a particular logical block address  302  has a content-based mapping type or an address-based mapping type. For example, the CAS/LBA flag  304  may be a binary flag such that, e.g., a value of 1 may indicate that the corresponding logical address has a content-based mapping type and a value of 0 may indicate that the corresponding logical address has the address-based mapping type. Any other values or mechanisms may be used to indicate the type of the mapping. 
     As described above, a content-based mapping of logical block addresses to physical addresses provides many benefits including more efficient deduplication, storage space savings, and other similar benefits. However, in some cases where the underlying data is not easily deduplicated, such as, e.g., encrypted data, a large amount of memory may be used in mapping the logical addresses to the physical addresses using content-based mapping, potentially resulting in a reduction in the total available addressable space and reduced access speeds. Illustrative embodiments utilize mapping tables that include both content-based mapping for logical block addresses for which the associated data can be deduplicated and address-based mapping for logical block addresses for which the associated data is not easily deduplicated. 
     The second level of mapping using the HMD table, illustrated in  FIG. 3B  as a H2D table  308 , associates respective ones of the hash values with respective physical storage locations in one or more of the storage devices  106 . This is also referred to as physical layer mapping. For example, as illustrated in  FIG. 3B , an entry in the H2D table  308  may include a hash value  310 , a reference count  312 , and a physical offset for the data page  314 . In some embodiments, the hash value  310  may be used as a key for accessing the entries in the H2D table. 
     In illustrative embodiments, for example, the hash value  310  may be a hash handle or other content-based signature generated based on a data page associated with a logical block address having the content-based mapping type or may be a hash of the logical block address itself for logical block addresses having the address-based mapping type. 
     For a given write request, both of the corresponding H2D and A2H tables are updated in conjunction with the processing of that write request. 
     The A2H and H2D tables described above are examples of what are more generally referred to herein as “mapping tables” of respective first and second distinct types. Other types and arrangements of mapping tables or other content-based signature mapping information may be used in other embodiments. 
     Such mapping tables are still more generally referred to herein as “metadata structures” of the content addressable storage system  105 . It should be noted that additional or alternative metadata structures can be used in other embodiments. References herein to particular tables of particular types, such as A2H, H2D, and HMD tables, and their respective configurations, should be considered non-limiting and are presented by way of illustrative example only. 
     The logical block addresses or LBAs of a logical layer of the content addressable storage system  105  correspond to respective physical blocks of a physical layer of the content addressable storage system  105 . The user data pages of the logical layer are organized by LBA and are referenced via respective hash values  306 / 310  to particular physical blocks of the physical layer using the A2H and HMD tables. 
     Each of the physical blocks has an associated reference count, e.g., a reference count  312 , that is maintained within the content addressable storage system  105 , e.g., within the H2D table. The reference count for a given physical block indicates the number of logical blocks that point to that same physical block, e.g., the block found at the corresponding physical offset  314  in the H2D table. 
     In some embodiments, logical block addresses having the address-based mapping type may be mapped via the A2H and H2D tables to a region or range of physical addresses. For example, a single logical block address having the address-based mapping type may map to an entire stripe in a RAID 6 array or any other range of physical addresses. In some embodiments, the single logical block address may correspond to a first logical block address in a range of logical block addresses and may map to a first physical address in a range of physical addresses. In such an embodiment, data corresponding to a particular logical block address in the range of logical block addresses may be accessed by utilizing the entry corresponding to the first logical block address in the range of logical block addresses in the A2H table and the corresponding entry in the H2D table to identify the first physical address in the range of physical addresses. For example, the offset of the particular logical block address relative to the first logical block address may be used as the offset of the corresponding physical address relative to the first physical address. In this manner fewer entries are needed in the A2H and H2D tables to provide access to the physical addresses for non-deduplicatable data. For example, by mapping a range of logical block addresses having the address-based mapping type to a range of physical addresses based on a single entry in each of the A2H and H2D tables, the size of the A2H and H2D tables may be reduced which allows more storage space to be available as usable data storage. 
     As an example, for a region or range of logical block addresses having a size of 2 MB, the A2H table may include an entry only for the first logical block address, e.g., addr1, of that region with a corresponding hash value generated based on the first logical block address, e.g., hashed(addr1). The H2D table may then map the hash value generated based on the first logical address, e.g., hashed(addr1), to a corresponding physical address which represents a first physical address in a region or range of physical addresses allocated for the region or range of logical addresses, e.g., physical location(hashed(addr1)). If an IO operation reads from a logical block address addr1+N, then the data will be read from physical location physical location(hashed(addr1))+N, where N is used as the offset for both the logical address range and the physical address range. 
     In some embodiments, for example, the A2H table  300  may include the same hash value  306  for more than one logical block address having the address-based mapping type where, for example, the same hash value  306  may be used for every logical block address in a range of logical block addresses having the address-based mapping type. 
     In some embodiments, entries in the A2H table including logical block addresses having the address-based mapping type may alternatively include a pointer directly to the corresponding physical address instead of the hash value that is mapped separately to the physical address via the H2D table. For example, in such an embodiment, the H2D table may be circumvented entirely for those logical block addresses having the address-based mapping type, thereby reducing the memory required for the H2D table. 
     In releasing logical address space in the storage system, a dereferencing operation is generally executed for each of the LBAs being released. More particularly, the reference count of the corresponding physical block is decremented. A reference count of zero indicates that there are no longer any logical blocks that reference the corresponding physical block, and so that physical block can be released. 
     It should also be understood that the particular arrangement of storage controller processing modules  108 C,  108 D,  108 R and  108 M as shown in the  FIG. 1  embodiment is presented by way of example only. Numerous alternative arrangements of processing modules of a distributed storage controller may be used to implement functionality for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings in a clustered storage system in other embodiments. 
     Additional examples of content addressable storage functionality implemented in some embodiments by control modules  108 C, data modules  108 D, routing modules  108 R and management module(s)  108 M of distributed storage controller  108  can be found in U.S. Pat. No. 9,104,326, entitled “Scalable Block Data Storage Using Content Addressing,” which is incorporated by reference herein. Alternative arrangements of these and other storage node processing modules of a distributed storage controller in a content addressable storage system can be used in other embodiments. 
     As indicated previously, the host devices  102  and content addressable storage system  105  in the  FIG. 1  embodiment are assumed to be implemented using at least one processing platform each comprising one or more processing devices each having a processor coupled to a memory. Such processing devices can illustratively include particular arrangements of compute, storage and network resources. 
     The host devices  102  and the content addressable storage system  105  may be implemented on respective distinct processing platforms, although numerous other arrangements are possible. For example, in some embodiments at least portions of the host devices  102  and the content addressable storage system  105  are implemented on the same processing platform. The content addressable storage system  105  can therefore be implemented at least in part within at least one processing platform that implements at least a one of the host devices  102 . 
     The term “processing platform” as used herein is intended to be broadly construed so as to encompass, by way of illustration and without limitation, multiple sets of processing devices and associated storage systems that are configured to communicate over one or more networks. For example, distributed implementations of the system  100  are possible, in which certain components of the system reside in one data center in a first geographic location while other components of the system reside in one or more other data centers in one or more other geographic locations that are potentially remote from the first geographic location. Thus, it is possible in some implementations of the system  100  for the host devices  102  and the content addressable storage system  105  to reside in different data centers. Numerous other distributed implementations of the host devices  102  and/or the content addressable storage system  105  are possible. Accordingly, the content addressable storage system  105  can also be implemented in a distributed manner across multiple data centers. 
     Additional examples of processing platforms utilized to implement host devices and/or storage systems in illustrative embodiments will be described in more detail below in conjunction with  FIGS. 8 and 9 . 
     It is to be appreciated that these and other features of illustrative embodiments are presented by way of example only, and should not be construed as limiting in any way. 
     Accordingly, different numbers, types and arrangements of system components such as host devices  102 , network  104 , content addressable storage system  105 , storage devices  106 , storage controllers  108  and storage nodes  115  can be used in other embodiments. 
     It should be understood that the particular sets of modules and other components implemented in the system  100  as illustrated in  FIG. 1  are presented by way of example only. In other embodiments, only subsets of these components, or additional or alternative sets of components, may be used, and such components may exhibit alternative functionality and configurations. 
     For example, in some embodiments, at least portions of the functionality for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings as disclosed herein can be implemented in a host device, in a storage system, or partially in a host device and partially in a storage system. Illustrative embodiments are therefore not limited to arrangements in which all such functionality is implemented in a host device or a storage system, and therefore encompass various hybrid arrangements in which the functionality is distributed over one or more host devices and one or more storage systems, each comprising one or more processing devices. 
     Referring now to  FIG. 2 , a more detailed view of a portion of the distributed storage controller  108  in an illustrative embodiment is shown. This embodiment illustrates an example arrangement of control modules  108 C, data modules  108 D and a management module  108 M of the distributed storage controller  108 . It is assumed in this embodiment that these and possibly other modules of the distributed storage controller  108  are interconnected in a full mesh network, such that each of the modules can communicate with each of the other modules, although other types of networks and different module interconnection arrangements can be used in other embodiments. 
     The management module  108 M of the distributed storage controller  108  in this embodiment more particularly comprises a system-wide management module or SYM module of the type mentioned previously. Although only a single SYM module is shown in this embodiment, other embodiments can include multiple instances of the SYM module possibly implemented on different ones of the storage nodes. It is therefore assumed that the distributed storage controller  108  comprises one or more management modules  108 M. 
     A given instance of management module  108 M comprises address mapping logic  200  and associated management program code  202 . The management module  108 M communicates with control modules  108 C- 1  through  108 C-x, also denoted as C-module  1  through C-module x. The control modules  108 C communicate with data modules  108 D- 1  through  108 D-y, also denoted as D-module  1  through D-module y. The variables x and y are arbitrary integers greater than one, and may but need not be equal. In some embodiments, each of the storage nodes  115  of the content addressable storage system  105  comprises one of the control modules  108 C and one of the data modules  108 D, as well as one or more additional modules including one of the routing modules  108 R. A wide variety of alternative configurations of nodes and processing modules are possible in other embodiments. Also, the term “storage node” as used herein is intended to be broadly construed, and may comprise a node that implements storage control functionality but does not necessarily incorporate storage devices. 
     The control modules  108 C- 1  through  108 C-x in the  FIG. 2  embodiment comprise respective sets of mapping tables  204 C- 1  through  204 C-x, e.g., sets of A2H and H2D tables. The A2H tables are utilized to store address-to-hash mapping information and the H2D tables are utilized to store hash-to-data mapping information, in support of mapping of logical addresses for respective pages to corresponding physical addresses for those pages via respective hashes or other types of content-based or address-based signatures, as described in further detail elsewhere herein. The control modules  108 C- 1  through  108 C-x further comprise corresponding instances of control logic  206 C- 1  through  206 C-x that interact with the address mapping logic  200  of the management module  108 M to support determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings as disclosed herein. While described as being included in the control modules  108 C, in some embodiments, some or all of the mapping tables  204 C may also or alternatively be included in other modules of the controller  108  such as, e.g., the data modules  108 D. For example, in some embodiments, the A2H tables may be included in the control modules  108 C while the H2D tables may be included in the data modules  108 D. Any other arrangement for the mapping tables  204 C may also or alternatively be used. 
     The control modules  108 C may further comprise additional components not explicitly shown in  FIG. 2 , such as respective messaging interfaces that are utilized by the control modules  108  to generate control-to-routing messages for transmission to the routing modules  108 R, and to process routing-to-control messages received from the routing modules  108 R. Such messaging interfaces can also be configured to generate messages for transmission to the management module  108 M and to process instructions and other messages received from the management module  108 M. 
     The data modules  108 D- 1  through  108 D-y in the  FIG. 2  embodiment comprise respective control interfaces  210 D- 1  through  210 D-y. These control interfaces  210 D support communication between the data modules  108 D and corresponding ones of the control modules  108 C. Also included in the data modules  108 D- 1  through  108 D-y are respective SSD interfaces  212 D- 1  through  212 D-y. These SSD interfaces  212 D support communications with corresponding ones of the storage devices  106 . As mentioned above, in some embodiments, some or all of the mapping tables  204 C may also or alternatively be included in the data modules  108 D. 
     An example system diagram utilizing both content-based and address-based mapping between logical addresses and physical addresses is illustrated in  FIG. 4 . For example, a logical layer  400  may comprise copy data management, thin clones (read-write copies of thin block storage resources such as, e.g., LUNs, consistency groups, virtual machine file system (VMFS) datastores, or other similar thin block storage resource), volumes, snapshots, data and metadata (data/MD) read cache, native replication or other types of data. The data found in the logical block addresses of the logical layer may be of a content-based mapping type, e.g., CAS  402 , or an address-based mapping type, e.g., LBA  404 . For example, the logical block addresses of each mapping type may be used as keys for entries in the A2H table with the CAS/LBA flag  304  ( FIG. 3A ) indicating which type of mapping is being used. Each of the CAS  402  and LBA  404  type entries may correspond to a handle  406 , e.g., a hash value  306  as described above. The handle  406  is mapped to a physical address in the capacity pool  408 , for example, using the H2D table as described above. 
     The operation of the information processing system  100  will now be described in further detail with reference to the flow diagram of  FIG. 5 . The flow diagram of  FIG. 5  illustrates a set of processing operations implementing functionality for utilizing both content-based and address-based mapping between logical addresses and physical addresses in a content addressable storage system. The process includes steps  500  through  510 , and is suitable for use in system  100  but is more generally applicable to other types of systems in which it is desirable to utilize both content-based and address-based mapping between logical addresses and physical addresses. The steps of the flow diagram are illustratively performed at least in part under the control of a storage controller of a storage system, such as the distributed storage controller  108  of content addressable storage system  105 . 
     In step  500 , a plurality of logical addresses are received by the storage controller  108 . For example, a host device may issue one or more 10 requests corresponding to data associated with the plurality of logical addresses. 
     In step  502 , the storage controller  108  determines whether a given logical address has a content-based mapping type or an address-based mapping type, for example, using the CAS/LBA flag  304  ( FIG. 3A ) mentioned above. 
     In step  504 , responsive to the storage controller  108  determining that the given logical address has the content-based mapping type, the storage controller  108  utilizes a mapping generated based on a content of a data page associated with the given logical address to identify a corresponding physical address, for example, as described above with reference to the A2H and 
     H2D tables. 
     In step  506 , responsive to the storage controller  108  determining that the given logical address has the address-based mapping type, the storage controller  108  utilizes a mapping generated based on the given logical address to identify a corresponding physical address, for example, as described above with reference to the A2H and H2D tables. 
     In step  508 , storage controller  108  accesses the data page at the identified corresponding physical address to perform an IO operation, e.g., a read or a write, according to the IO request. 
     In step  510 , storage controller  108  determines whether or not any of the received logical addresses remain to be processed for the IO request. If there are logical addresses that still need to be processed, the method returns to step  502 . If none of the received logical addresses remain to be processed, the method ends as shown. 
     In some embodiments, a host device  102  may provide information to the storage controller  108  that indicates whether target data is of a non-deduplicatable type, e.g., encrypted data, or of a deduplicatable type, e.g., non-encrypted data. Target data may comprise, for example, data associated with an IO request, data currently stored on storage devices  106 , or any other data that is or will be stored on the storage devices  106 . 
     In some embodiments, for example, host devices  102 - 1 ,  102 - 2 , . . .  102 -N may further include respective drivers  103 - 1 ,  103 - 2 , . . .  103 -N that determine whether target data is of the non-deduplicatable type or of the deduplicatable type. In some embodiments, each host device  102  may comprise one or more drivers  103 . In some embodiments, a subset of host devices  102  may comprise one or more drivers  103  or only one of the host devices  102  may comprise one or more drivers  103 . 
     The flow diagram of  FIG. 6  illustrates a set of processing operations implementing functionality for drivers  103  in an illustrative embodiment. The flow diagram of  FIG. 7  illustrates a set of processing operations implementing functionality for a storage controller  108  in an illustrative embodiment. The process of  FIG. 6  includes steps  600  through  604  and the process of  FIG. 7  includes steps  700  through  708 . The processes of  FIGS. 6 and 7  are suitable for use in system  100  but are more generally applicable to other types of systems in which it is desirable to utilize both content-based and address-based mapping between logical addresses and physical addresses for respective deduplicatable types of data and non-deduplicatable types of data. 
     The steps of the flow diagram of  FIG. 6  are illustratively performed at least in part under the control of a host device of an information processing system, such as, e.g., a host device  102 . Some or all of the functionality for drivers  106  found in the flow diagram of  FIG. 6  may also or alternatively be implemented by a storage controller  108  of SAN  105 . The steps of the flow diagram of  FIG. 7  are illustratively performed at least in part under the control of a storage controller of a storage system, such as, e.g., storage controller  108 . Some or all of the functionality for storage controller  108  found in the flow diagram of  FIG. 7  may also or alternatively be implemented by a host device  102  of information processing system  100 . 
     At  600 , a given driver  103  determines whether target data, e.g., data associated with an IO request, data residing on storage devices  106 , or other similar data, is of a non-deduplicatable type or a deduplicatable type. In some embodiments, for example, the given driver  103  may be hosted in a virtual machine which integrates with a hypervisor or other database technology, such as, e.g., an Oracle® API, a VMware® Elastic Sky X (ESX®) API, or other similar technology, to determine which other virtual machines running on such system, or other data of such a system comprise non-deduplicatable data, such as, e.g., encrypted data. The determination of whether target data is of the deduplicatable type or non-deduplicatable type will be described in more detail below. 
     At  602 , the given driver  103  generates information based on the determination that indicates whether the target data is of the non-deduplicatable type or the deduplicatable type, as will be described in more detail blow. 
     At  604 , the given driver  103  provides the information to the SAN  105 , e.g., to storage controller  108 . The method then ends. 
     At  700 , the storage controller  108  receives the information indicating whether target data is of the non-deduplicatable type or the deduplicatable type and determines the type of the target data based on the information at  702 . 
     If the storage controller  108  determines that the type of the target data is the deduplicatable type, the storage controller utilizes a mapping generated based on content of the target data to identify a corresponding physical address at which to store the target data at  704 . For example, the storage controller  108  may utilize the content-based mapping, as described above. The method then proceeds to step  706 . 
     Referring back to step  702 , if the storage controller  108  determines that the type of the target data is the non-deduplicatable type, the storage controller utilizes a mapping generated based on logical address associated with the target data to identify a corresponding physical address at which to store the target data at  708 . For example, the storage controller  108  may utilize the address-based mapping, as described above. The method then proceeds to step  706 . 
     At  706 , the storage controller  108  stores the target data at the identified physical address, e.g., a physical address identified based on a content-based mapping for data of the deduplicatable type, or a physical address identified based on an address-based mapping for data of the non-deduplicatable type. The method then ends. 
     In some embodiments, the given driver  103  may periodically provide to the storage controller  108  the information indicating which portions of a drive are non-deduplicatable and thus should be stored in an address-based portion of the storage, for example, as described above with reference to  FIGS. 1-5 , and which portions are deduplicatable, e.g., not encrypted, and should be stored in the content-based storage. In some embodiments, data stored in the content-based portion of the storage may be moved to the address-based portion of the storage in response to the information indicating that the data is of the non-deduplicatable type. 
     In one example implementation of the functionality of the processes of  FIGS. 6 and 7 , in an ESX® environment, a virtual machine hosting a given driver  103  may connect to a management utility which manages virtual machines such as, e.g., VMware VCenter®, and determine which other virtual machines in the ESX® environment comprise non-deduplicatable data, e.g., are encrypted. The virtual machine may also identify virtual disks corresponding to the encrypted virtual machines. Each virtual disk resides on a portion of SAN  105  and is mapped to one or more logical volumes on the content-based portion of the SAN  105 . 
     In such an example embodiment, the given driver  103  determines which blocks associated with the corresponding virtual disks on the SAN  105  are encrypted by obtaining and attaching a snapshot of the mapped logical volumes to the virtual machine hosting the given driver  103 . The virtual machine hosting the driver  103  parses the virtual machine file system (VMFS) to understand which blocks in the mapped logical volume belong to the virtual machines having non-deduplicatable data and provides information to the storage controller  108  indicating which blocks comprise non-deduplicatable data, e.g., encrypted data in this example. For example, a command may be sent to the storage controller, e.g., using a control path API, that comprises the information indicating which blocks comprise the non-deduplicatable data. The storage controller  108  may then move the relevant blocks of non-deduplicatable data from a physical address determined based on the above described content-based mapping to a physical address determined based on the above described address-based mapping. This may be considered an out of band determination and reporting of the information. 
     In one example implementation of the functionality of the processes of  FIGS. 6 and 7 , in an Oracle® database environment, the virtual machine hosting the driver  103  may identify files of the database that correspond to non-deduplicatable data, e.g., encrypted tables or tables comprising encrypted fields, and may obtain one or more blocks of the SAN  105  based on a mapping of the corresponding logical volumes for those files to the one or more blocks. The driver  103  parses the blocks to determine which of the blocks for those files comprise the non-deduplicatable data, e.g., encrypted data, and provides the information indicating to the storage controller  108  that these blocks comprise data of the non-deduplicatable type. For example, a command may be sent to the storage controller, e.g., using a control path API, that comprises the information indicating which blocks comprise the non-deduplicatable data. The storage controller  108  may then move this data to the address-based portion of the SAN  105 , as described above. This may also be considered an out of band determination and reporting of the information. 
     In one example implementation of the functionality of the processes of  FIGS. 6 and 7 , the given driver  103  may also or alternatively execute at a kernel level of the host device. For example, the given driver  103  may run inside an ESX® kernel, e.g., in the virtual SCSI (VSCSI) layer, and may intercept any IO requests, for example, IO requests from a virtual machine comprising non-deduplicatable data, e.g., an encrypted virtual machine. 
     The given driver  103  may add the information to the IO request, for example, by setting a portion of the IO request to indicate that some or all of the data associated with the IO request is of the non-deduplicatable type. For example, in some embodiments, the IO request may comprise an SCSI message and the given driver  103  may set a portion of the SCSI message, e.g., a portion of the command descriptor block (CDB) of the SCSI message, to indicate that the associated data comprises data of the non-deduplicatable type. As an example, the given driver  103  may add or set one or more bits of the SCSI message, such as, e.g., one or more bits of the CDB, or in some embodiments, one bit of the CDB, based on whether the data is of the non-deduplicatable type or the deduplicatable type. As an example, if a particular bit of the CDB is set to 1, that may indicate to the storage controller  108  that the data is of the non-deduplicatable type while if the particular bit is set to 0, that may indicate to the storage controller  108  that the data is of the deduplicatable type, or vice versa. This may be considered an in-band determination and reporting of the information. 
     The storage controller  108  obtains the intercepted IO request from the host device  102  including the SCSI message and determines based on the set portion of the SCSI message whether the associated data is of the non-deduplicatable type or the deduplicatable type. The storage controller  108  may then store the associated data accordingly, e.g., store the associated data of the deduplicatable type according to the above described content-based mapping, and store associated data of the non-deduplicatable type according to the above described address-based mapping. 
     In another example embodiment, the given driver  103  is implemented at the file system level of an Oracle® database and intercepts IO requests that are targeted at files, tables or table fields comprising non-deduplicatable data, e.g., encrypted files, encrypted tables, or encrypted table fields, and adds the above described information to the SCSI message. For example, the given driver  103  may set a portion of the SCSI message to indicate the type of the data. The portion may comprise, for example, a portion of the CDB of the SCSI message, such as, e.g., one or more bits of the CDB or even a single bit of the CDB. 
     The particular processing operations and other system functionality described above in conjunction with the flow diagrams of  FIGS. 5-7  are presented by way of illustrative examples only, and should not be construed as limiting the scope of the disclosure in any way. Alternative embodiments can use other types of processing operations for implementing functionality for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings. For example, the ordering of the process steps may be varied in other embodiments, or certain steps may be performed at least in part concurrently with one another rather than serially. Also, one or more of the process steps may be repeated periodically, or multiple instances of the process can be performed in parallel with one another in order to handle multiple page ranges and associated metadata within a given storage system. 
     Functionality such as that described in conjunction with the flow diagrams of  FIGS. 5-7  can be implemented at least in part in the form of one or more software programs stored in memory and executed by a processor of a processing device such as a computer or server. As will be described below, a memory or other storage device having executable program code of one or more software programs embodied therein is an example of what is more generally referred to herein as a “processor-readable storage medium.” 
     A storage controller such as distributed storage controller  108  that is configured to control performance of one or more steps of the process of the flow diagrams of  FIGS. 5-7  in system  100  can be implemented as part of what is more generally referred to herein as a processing platform comprising one or more processing devices each comprising a processor coupled to a memory. A given such processing device may correspond to one or more virtual machines or other types of virtualization infrastructure such as Docker containers or Linux containers (LXCs). The host devices  102  and content addressable storage system  105  of system  100 , as well as other system components, may be implemented at least in part using processing devices of such processing platforms. For example, in the distributed storage controller  108 , respective distributed modules can be implemented in respective containers running on respective ones of the processing devices of a processing platform. 
     Illustrative embodiments of storage systems with functionality for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings as disclosed herein can provide a number of significant advantages relative to conventional arrangements. 
     For example, some embodiments provide content addressable storage systems and other types of clustered storage systems that are configured to utilize both content-based and address-based mapping between logical addresses and physical addresses which may provide more efficient use of storage space for metadata. For example, by using address-based mapping for data that is not easily deduplicated, and in some embodiments having a single logical block address map to a range or region of physical addresses such as an entire RAID stripe, the amount of metadata required in the H2D table for mapping data that is not easily deduplicated may be reduced, thereby increasing the amount of data available for other storage tasks or for the storage of additional data. In addition, because the host device in illustrative embodiments provides type information about target data to the storage controller, e.g., a deduplicatable type or a non-deduplicatable type, the storage controller may efficiently determine whether to use address-based mappings (e.g., for the non-deduplicatable type of data) or content-based mappings (e.g., for the deduplicatable type of data) for the target data, thereby reducing the processing resources required by the storage controller for processing IO requests and determining which type of mapping to use. 
     It is to be appreciated that the particular advantages described above and elsewhere herein are associated with particular illustrative embodiments and need not be present in other embodiments. Also, the particular types of information processing system features and functionality as illustrated in the drawings and described above are exemplary only, and numerous other arrangements may be used in other embodiments. 
     Illustrative embodiments of processing platforms utilized to implement functionality for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings will now be described in greater detail with reference to  FIGS. 8 and 9 . Although described in the context of system  100 , these platforms may also be used to implement at least portions of other information processing systems in other embodiments. 
       FIG. 8  shows an example processing platform comprising cloud infrastructure  800 . The cloud infrastructure  800  comprises a combination of physical and virtual processing resources that may be utilized to implement at least a portion of the information processing system  100 . The cloud infrastructure  800  comprises multiple virtual machines and/or container sets  802 - 1 ,  802 - 2 , . . .  802 -L implemented using virtualization infrastructure  804 . The virtualization infrastructure  804  runs on physical infrastructure  805 , and illustratively comprises one or more hypervisors and/or operating system level virtualization infrastructure. The operating system level virtualization infrastructure illustratively comprises kernel control groups of a Linux operating system or other type of operating system. 
     The cloud infrastructure  800  further comprises sets of applications  810 - 1 ,  810 - 2 , . . .  810 -L running on respective ones of the VMs/container sets  802 - 1 ,  802 - 2 , . . .  802 -L under the control of the virtualization infrastructure  804 . The VMs/container sets  802  may comprise respective VMs, respective sets of one or more containers, or respective sets of one or more containers running in VMs. 
     In some implementations of the  FIG. 8  embodiment, the VMs/container sets  802  comprise respective VMs implemented using virtualization infrastructure  804  that comprises at least one hypervisor. Such implementations can provide storage functionality of the type described above for one or more processes running on a given one of the VMs. 
     An example of a hypervisor platform that may be used to implement a hypervisor within the virtualization infrastructure  804  is the VMware® vSphere® which may have an associated virtual infrastructure management system such as the VMware® vCenter™. The underlying physical machines may comprise one or more distributed processing platforms that include one or more storage systems. 
     In other implementations of the  FIG. 8  embodiment, the VMs/container sets  802  comprise respective containers implemented using virtualization infrastructure  804  that provides operating system level virtualization functionality, such as support for Docker containers running on bare metal hosts, or Docker containers running on VMs. The containers are illustratively implemented using respective kernel control groups of the operating system. Such implementations can provide storage functionality of the type described above for one or more processes running on different ones of the containers. For example, a container host device supporting multiple containers of one or more container sets can implement one or more instances of the processes of  FIGS. 5-7  for determining a type of target data and indicating the type to the storage controller for storage of the target data based on content-based or address-based mappings. 
     As is apparent from the above, one or more of the processing modules or other components of system  100  may each run on a computer, server, storage device or other processing platform element. A given such element may be viewed as an example of what is more generally referred to herein as a “processing device.” The cloud infrastructure  800  shown in  FIG. 8  may represent at least a portion of one processing platform. Another example of such a processing platform is processing platform  900  shown in  FIG. 9 . 
     The processing platform  900  in this embodiment comprises a portion of system  100  and includes a plurality of processing devices, denoted  902 - 1 ,  902 - 2 ,  902 - 3 , . . .  902 -K, which communicate with one another over a network  904 . 
     The network  904  may comprise any type of network, including by way of example a global computer network such as the Internet, a WAN, a LAN, a satellite network, a telephone or cable network, a cellular network, a wireless network such as a WiFi or WiMAX network, or various portions or combinations of these and other types of networks. 
     The processing device  902 - 1  in the processing platform  900  comprises a processor  910  coupled to a memory  912 . 
     The processor  910  may comprise a microprocessor, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a graphics processing unit (GPU) or other type of processing circuitry, as well as portions or combinations of such circuitry elements. 
     The memory  912  may comprise random access memory (RAM), read-only memory (ROM), flash memory or other types of memory, in any combination. The memory  912  and other memories disclosed herein should be viewed as illustrative examples of what are more generally referred to as “processor-readable storage media” storing executable program code of one or more software programs. 
     Articles of manufacture comprising such processor-readable storage media are considered illustrative embodiments. A given such article of manufacture may comprise, for example, a storage array, a storage disk or an integrated circuit containing RAM, ROM, flash memory or other electronic memory, or any of a wide variety of other types of computer program products. The term “article of manufacture” as used herein should be understood to exclude transitory, propagating signals. Numerous other types of computer program products comprising processor-readable storage media can be used. 
     Also included in the processing device  902 - 1  is network interface circuitry  914 , which is used to interface the processing device with the network  904  and other system components, and may comprise conventional transceivers. 
     The other processing devices  902  of the processing platform  900  are assumed to be configured in a manner similar to that shown for processing device  902 - 1  in the figure. 
     Again, the particular processing platform  900  shown in the figure is presented by way of example only, and system  100  may include additional or alternative processing platforms, as well as numerous distinct processing platforms in any combination, with each such platform comprising one or more computers, servers, storage devices or other processing devices. 
     For example, other processing platforms used to implement illustrative embodiments can comprise converged infrastructure such as VxRail™, VxRack™, VxRack™ FLEX, VxBlock™ or Vblock® converged infrastructure from VCE, the Virtual Computing Environment Company, now the Converged Platform and Solutions Division of Dell EMC. 
     It should therefore be understood that in other embodiments different arrangements of additional or alternative elements may be used. At least a subset of these elements may be collectively implemented on a common processing platform, or each such element may be implemented on a separate processing platform. 
     As indicated previously, components of an information processing system as disclosed herein can be implemented at least in part in the form of one or more software programs stored in memory and executed by a processor of a processing device. For example, at least portions of the storage functionality of one or more components of a host device or storage system as disclosed herein are illustratively implemented in the form of software running on one or more processing devices. 
     It should again be emphasized that the above-described embodiments are presented for purposes of illustration only. Many variations and other alternative embodiments may be used. For example, the disclosed techniques are applicable to a wide variety of other types of information processing systems, host devices, storage systems, storage nodes, storage devices, storage controllers, and associated control logic. Also, the particular configurations of system and device elements and associated processing operations illustratively shown in the drawings can be varied in other embodiments. Moreover, the various assumptions made above in the course of describing the illustrative embodiments should also be viewed as exemplary rather than as requirements or limitations of the disclosure. Numerous other alternative embodiments within the scope of the appended claims will be readily apparent to those skilled in the art.