Patent Publication Number: US-10768829-B2

Title: Opportunistic use of streams for storing data on a solid state device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 62/459,426 filed on Feb. 15, 2017, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Solid state devices (SSDs), such as flash storage, offer benefits over traditional hard disk drives (HDDs). For example, SSDs are often faster, quieter and draw less power than their HDD counterparts. However, there are also drawbacks associated with SSDs. For example, SSDs are limited in the sense that data can only be erased from the storage device in blocks, also known as “erase blocks.” These blocks may contain, in addition to data that a user wishes to erase, important data that the user wishes to keep stored on the SSD. In order to erase the unwanted data, the SSD must perform a process known as “garbage collection” in order to move data around on the SSD so that important files are not accidentally deleted. However, this process may result in an effect known as “write amplification” where the same data is written to the physical media on the SSD multiple times, shortening the lifespan of the SSD. Streaming is a process by which data stored on the SSD may be grouped together in a stream comprising one or more erase blocks based, for example, on an estimated deletion time of all of the data in the stream. By storing data that is likely to be deleted together in the same erase block or group of erase blocks (i.e., the same stream), a number of the problems associated with SSD storage may be alleviated. 
     SUMMARY 
     Methods and systems are disclosed herein for optimizing the use of streams by performing a combination of stream and non-stream writes based on a size of the data being written to the stream. For example, a method may comprise writing data associated with a plurality of files to a first set of one or more erase blocks not associated with a stream, determining that an amount of data associated with a given one of the plurality of files in the first set of one or more erase blocks has reached a threshold, and moving the data associated with the given file from the first set of one or more erase blocks to a stream, the stream comprising a second set of one or more erase blocks different from the first set of one or more erase blocks, the first set of one or more erase blocks and the second set of one or more erase blocks being located on a storage device. In one embodiment, a file system associated with a computing device may be configured to copy the data to the host memory, re-write the data to a stream on the storage device and to update metadata maintained by the file system to account for the new location of the data. In a second embodiment, the storage device may be configured to receive a stream identifier associated with the stream, copy the data associated with the given file from the first set of one or more erase blocks to the stream, and to update metadata maintained by the storage device to account for the new location of the data on the storage device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing Summary, as well as the following Detailed Description, is better understood when read in conjunction with the appended drawings. In order to illustrate the present disclosure, various aspects of the disclosure are shown. However, the disclosure is not limited to the specific aspects discussed. In the drawings: 
         FIG. 1  illustrates an example computing device, in which the aspects disclosed herein may be employed; 
         FIG. 2  illustrates an example solid state device (SSD); 
         FIGS. 3A-3D  illustrate a process of garbage collection performed on the SSD; 
         FIG. 4  illustrates a process of streaming multiple erase blocks on a device, for example, on an SSD; 
         FIG. 5  illustrates an example architecture for implementing streaming functionality on a device; 
         FIG. 6  illustrates an example method for optimizing the use of available streams on a storage device; 
         FIG. 7  illustrates a method of writing data associated with a number of files to an erase block in a non-stream manner; 
         FIG. 8  illustrates the continued writing data associated with a number of files to a second erase block in a non-stream manner; 
         FIG. 9  illustrates a method of moving the data associated with a given file from a group of one or more erase blocks to a stream; 
         FIG. 10  illustrates a method of writing additional data associated with the given file to the stream; 
         FIG. 11  illustrates a method of writing data associated with the given file in a non-stream manner in response to a determination that the stream is full; 
         FIG. 12  illustrates a file system implementing the method for optimizing the use of available streams on the storage device; and 
         FIG. 13  illustrates a storage device implementing the method for optimizing the use of available streams on the storage device. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein are methods and systems for optimizing the number of stream writes to a storage device based, for example, on an amount of data associated with a given file and a size of available streams on the storage device. For example, a method may comprise writing data associated with a plurality of files to a first set of one or more erase blocks, determining that an amount of data associated with a given one of the plurality of files in the first set of one or more erase blocks has reached a threshold, and moving the data associated with the given file from the first set of one or more erase blocks to a stream, the stream comprising a second set of one or more erase blocks on the storage device different from the first set of one or more erase blocks. 
       FIG. 1  illustrates an example computing device  112  in which the techniques and solutions disclosed herein may be implemented or embodied. The computing device  112  may be any one of a variety of different types of computing devices, including, but not limited to, a computer, personal computer, server, portable computer, mobile computer, wearable computer, laptop, tablet, personal digital assistant, smartphone, digital camera, or any other machine that performs computations automatically. 
     The computing device  112  includes a processing unit  114 , a system memory  116 , and a system bus  118 . The system bus  118  couples system components including, but not limited to, the system memory  116  to the processing unit  114 . The processing unit  114  may be any of various available processors. Dual microprocessors and other multiprocessor architectures also may be employed as the processing unit  114 . 
     The system bus  118  may be any of several types of bus structure(s) including a memory bus or memory controller, a peripheral bus or external bus, and/or a local bus using any variety of available bus architectures including, but not limited to, Industry Standard Architecture (ISA), Micro-Channel Architecture (MSA), Extended ISA (EISA), Intelligent Drive Electronics (IDE), VESA Local Bus (VLB), Peripheral Component Interconnect (PCI), Card Bus, Universal Serial Bus (USB), Advanced Graphics Port (AGP), Personal Computer Memory Card International Association bus (PCMCIA), Firewire (IEEE 1394), and Small Computer Systems Interface (SCSI). 
     The system memory  116  includes volatile memory  120  and nonvolatile memory  122 . The basic input/output system (BIOS), containing the basic routines to transfer information between elements within the computing device  112 , such as during start-up, is stored in nonvolatile memory  122 . By way of illustration, and not limitation, nonvolatile memory  122  may include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable ROM (EEPROM), or flash memory. Volatile memory  120  includes random access memory (RAM), which acts as external cache memory. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM). 
     Computing device  112  also may include removable/non-removable, volatile/non-volatile computer-readable storage media.  FIG. 1  illustrates, for example, secondary storage  124 . Secondary storage  124  includes, but is not limited to, devices like a magnetic disk drive, floppy disk drive, tape drive, Jaz drive, Zip drive, LS-100 drive, memory card (such as an SD memory card), or memory stick. In addition, secondary storage  124  may include storage media separately or in combination with other storage media including, but not limited to, an optical disk drive such as a compact disk ROM device (CD-ROM), CD recordable drive (CD-R Drive), CD rewritable drive (CD-RW Drive) or a digital versatile disk ROM drive (DVD-ROM). To facilitate connection of the secondary storage  124  to the system bus  118 , a removable or non-removable interface is typically used such as interface  126 . 
       FIG. 1  further depicts software that acts as an intermediary between users and the basic computer resources described in the computing device  112 . Such software includes an operating system  128 . Operating system  128 , which may be stored on secondary storage  124 , acts to control and allocate resources of the computing device  112 . Applications  130  take advantage of the management of resources by operating system  128  through program modules  132  and program data  134  stored either in system memory  116  or on secondary storage  124 . It is to be appreciated that the aspects described herein may be implemented with various operating systems or combinations of operating systems. As further shown, the operating system  128  includes a file system  129  for storing and organizing, on the secondary storage  124 , computer files and the data they contain to make it easy to find and access them. 
     A user may enter commands or information into the computing device  112  through input device(s)  136 . Input devices  136  include, but are not limited to, a pointing device such as a mouse, trackball, stylus, touch pad, keyboard, microphone, joystick, game pad, satellite dish, scanner, TV tuner card, digital camera, digital video camera, web camera, and the like. These and other input devices connect to the processing unit  114  through the system bus  118  via interface port(s)  138 . Interface port(s)  138  include, for example, a serial port, a parallel port, a game port, and a universal serial bus (USB). Output device(s)  140  use some of the same type of ports as input device(s)  136 . Thus, for example, a USB port may be used to provide input to computing device  112 , and to output information from computing device  112  to an output device  140 . Output adapter  142  is provided to illustrate that there are some output devices  140  like monitors, speakers, and printers, among other output devices  140 , which require special adapters. The output adapters  142  include, by way of illustration and not limitation, video and sound cards that provide a means of connection between the output device  140  and the system bus  118 . It should be noted that other devices and/or systems of devices provide both input and output capabilities such as remote computer(s)  144 . 
     Computing device  112  may operate in a networked environment using logical connections to one or more remote computing devices, such as remote computing device(s)  144 . The remote computing device(s)  144  may be a personal computer, a server, a router, a network PC, a workstation, a microprocessor based appliance, a peer device, another computing device identical to the computing device  112 , or the like, and typically includes many or all of the elements described relative to computing device  112 . For purposes of brevity, only a memory storage device  146  is illustrated with remote computing device(s)  144 . Remote computing device(s)  144  is logically connected to computing device  112  through a network interface  148  and then physically connected via communication connection  150 . Network interface  148  encompasses communication networks such as local-area networks (LAN) and wide-area networks (WAN). LAN technologies include Fiber Distributed Data Interface (FDDI), Copper Distributed Data Interface (CDDI), Ethernet, Token Ring and the like. WAN technologies include, but are not limited to, point-to-point links, circuit switching networks like Integrated Services Digital Networks (ISDN) and variations thereon, packet switching networks, and Digital Subscriber Lines (DSL). 
     Communication connection(s)  150  refers to the hardware/software employed to connect the network interface  148  to the bus  118 . While communication connection  150  is shown for illustrative clarity inside computing device  112 , it may also be external to computing device  112 . The hardware/software necessary for connection to the network interface  148  includes, for exemplary purposes only, internal and external technologies such as modems including regular telephone grade modems, cable modems and DSL modems, ISDN adapters, and Ethernet cards. 
     As used herein, the terms “component,” “system,” “module,” and the like are intended to refer to a computer-related entity, either hardware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a server and the server may be a component. One or more components may reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. 
       FIG. 2  illustrates an example solid state device (SSD)  200 . The SSD illustrated in  FIG. 2  may be, for example, a NAND flash storage device. The SSD  200  may, for example, be used to implement the secondary storage  124  of the example computing device shown in  FIG. 1 . As shown, the SSD may comprise a die  202 . A die may represent the smallest unit of the SSD that can independently execute commands. While the SSD in  FIG. 2  comprises only a single die, it is understood that an SSD may comprise any number of die. As further shown in  FIG. 2 , each die may comprise one or more planes  204 . An SSD may typically comprise one or two planes, and concurrent operations may take place on each plane. However, it is understood that an SSD may comprise any number of planes. As further illustrated in  FIG. 2 , each plane  204  may comprise a number of blocks  206 . A block may be the smallest unit of the SSD that can be erased. Blocks may also be referred to herein as “erase blocks.” Finally, as shown in  FIG. 2 , each block  206  may comprise a number of pages  208 . A page may be the smallest unit of the SSD that can be programmed. 
     Program operations on the SSD, also known as “writes” or “write operations,” may be made to any given page on the SSD. A page may be, for example, about 4-16 KB in size, although it is understood that any size may be used. In contrast, erase operations may be only be made at the block level. A block may be, for example, about 4-8 MB in size, although it is understood that any size may be used. A controller associated with the SSD may manage the flash memory and interface with the host system using a logical-to-physical mapping system, for example, logical block addressing (LBA). 
     SSDs generally do not allow for data stored in a given page to be updated. When new or updated data is saved to the SSD, the controller may be configured to write the new or updated data in a new location on the SSD and to update the logical mapping to point to the new physical location. This new location may be, for example, a different page within the same erase block, as further illustrated in  FIG. 3 . At this point, the data in the old location may no longer be valid, and may need to be erased before the location can be written to again. 
     However, as discussed above, the old or invalid data may not be erased without erasing all of the data within the same erase block. For example, that erase block may contain the new or updated data, as well as other data that a user may wish to keep stored on the SSD. In order to address this issue, the controller may be configured to copy or re-write all of the data that is not intended to be deleted to new pages in a different erase block. This may be referred to herein as “garbage collection.” The new or updated data may be written directly to a new page or may be striped across a number of pages in the new erase block. This undesirable process by which data is written to the SSD multiple times as a result of the SSDs inability to update data is known as write amplification, and is further illustrated below in connection with  FIG. 3 . Write amplification presents a significant problem in SSD storage as SSDs can only be programmed and erased a limited number of times. This may be referred to herein as the number of program/erase cycles that the SSD can sustain. 
     As shown in  FIG. 3A , an SSD may comprise two blocks: Block X and Block Y. It is understood that while the SSD illustrated in  FIGS. 3A-3D  comprises two blocks, an SSD may comprise any number of blocks. As discussed above, a block or “erase block” may comprise the smallest unit of the SSD that may be erased. Each of Block X and Block Y illustrated in  FIGS. 3A-3D  comprises sixteen pages, however, it is understood that a given block may comprise any number of pages. Data may be written directly to any one of the pages on Block X or Block Y. In addition, data may be striped across a plurality of pages associated with Block X or Block Y. As shown in  FIG. 3A , data may be written to Page A, Page B, Page C and Page D associated with Block X, while the remaining pages of Block X may be left empty (free). Block Y may similarly be left empty. 
     As shown in  FIG. 3B , additional data may be written to Block X at a later time via a write operation by the controller. Again, this write operation may comprise writing data directly to any one of the pages in Block X or Block Y or striping the data across a plurality of the pages. For example, data may be written directly to or striped across Page E, Page F, Page G, Page H, Page I, Page J, Page K and Page L associated with Block X. In addition, a user or application may wish to update the information stored at Pages A-D of  FIG. 3A . However, as discussed above, the SSD may not allow for data to be updated. Thus, in order to store the new data, a controller associated with the SSD may be configured to execute a write operation to additional pages in Block X representing the updates to Pages A-D. These pages, as illustrated in  FIG. 3B , may be labeled as Page A′, Page B′, Page C′ and Page D′. The data stored at Pages A′-D′ may represent any of minor or major updates to the data stored at Pages A-D. 
     As further illustrated in  FIG. 3C , in order to perform a delete operation on the data stored at Pages A-D, and as further discussed above, the entirety of Block X may need to be erased. The controller associated with the SSD may be configured to copy or re-write important data on Block X that the user does not wish to be deleted to a different erase block, for example, Block Y. As illustrated in  FIG. 3C , the controller may be configured to copy the data stored at Pages E-L as well as the data stored at Pages A′-D′ of Block X to Block Y. 
     As discussed above, this process of “updating” data to a new location may be referred to “garbage collection.” The process of garbage collection as illustrated in  FIG. 3C  may address the issue of erasing unwanted data while keeping important data stored on the device. However, this comes at the cost of copying and re-writing a single piece of data multiple times on the same SSD. For example, both Block X and Block Y of the SSD may contain copies of the data stored at Pages E-L as well as the data stored at Pages A′-D′. This undesirable process of re-writing multiple copies of the same data may be known as write amplification. 
     Finally, as shown in  FIG. 3D , the controller may be configured to erase all of the data stored at Block X. As all of the important data intended to be kept on the SSD has been copied to Block Y, the entirety of Block X may be deleted by the controller. Once this process has completed, the controller may be configured to write new data to any of the pages in Block X. However, as discussed above, this process of write amplification presents a significant problem in SSD storage as an SSD may only be programmed and erased a limited number of times. For example, in the case of a single level flash, the SSD may be written to and erased a maximum of 50,000-100,000 times. 
     One additional feature associated with SSD storage is the over-provisioning of storage space. Over-provisioning may be represented as the difference between the physical capacity of the flash memory and the logical capacity presented through the operating system as available for the user. During, for example, the process of garbage collection, the additional space from over-provisioning may help lower the write amplification when the controller writes to the flash memory. The controller may use this additional space to keep track of non-operating system data such as, for example, block status flags. Over-provisioning may provide reduced write amplification, increased endurance and increased performance of the SSD. However, this comes at the cost of less space being available to the user of the SSD for storage operations. 
     Solid state devices may support functionality known as “streaming” by which data may be associated with a particular stream based, for example, on an estimated deletion time of the data, in order to reduce the problems associated with write amplification and over-provisioning. A stream, as discussed herein, may comprise one or more erase blocks. The process of streaming SSDs may comprise, for example, instructing the SSD to associate a bunch of data together in the same erase block or group of erase blocks (i.e., in the same “stream”) because it is likely that all of the data will be erased at the same time. Because data that will be deleted together will be written to or striped across pages in the same erase block or group of erase blocks, the problems associated with write amplification and over-provisioning can be reduced. The process of streaming SSDs may be further illustrated as shown in connection with  FIG. 4 . 
     As shown in the example of  FIG. 4 , data may be grouped together in one or more erase blocks based, for example, on an estimated erase time of the data stored at each of the erase blocks. The controller may organize the one or more erase blocks such that data in each of the erase blocks may be erased together. This organization of data into one or more erase blocks based, for example, on an estimated deletion time of the data in the one or more erase blocks, may be referred to herein as “streaming.” As shown in  FIG. 4 , four erase blocks may be associated with Stream A, eight erase blocks may be associated with Stream B, and a single erase block may be associated with Stream C. The controller may be configured, for example, to perform all write operations of data that may be erased within two months to Stream A, all write operations of data that may be erased within two weeks to Stream B, and all write operations of data that may be erased within two days to Stream C. In another example, the controller may be configured to perform write operations to Stream A that may be erased upon the occurrence of an event that would result in all of the data written to Stream A being “updated” and subsequently marked as invalid. 
     A file system and a storage driver associated with a computing device may be provided with awareness of the “streaming” capability of an SSD in order to enable the file system and/or an application to take advantage of the streaming capability for more efficient storage. For example, a file system may be configured to receive a first request from an application to associate a file with a particular stream identifier available on a storage device, intercept one or more subsequent requests to write data to the file, associate the one or more subsequent requests with the stream identifier, and instruct a storage driver associated with the storage device to write the requested data to the identified stream. The file system may be further configured to store metadata associated with the file, the metadata comprising the stream identifier associated with the file. In addition, the file system may be configured to send to the application a plurality of stream parameters associated with the stream. The file system may be further configured, prior to associating the file with the stream identifier, to validate the stream identifier. 
       FIG. 5  is a block diagram illustrating example components of an architecture for implementing the streaming SSD functionality disclosed herein. As shown, in one embodiment, the architecture may comprise an application  502 , a file system  504 , a storage driver  506 , and a storage device  508 . 
     The application  502  may be configured to read and write files to the device  508  by communicating with the file system  504 , and the file system  504  may, in turn, communicate with the storage driver  506 . In order to take advantage of writing to a stream on the SSD, the application  502  may instruct the file system which ID to associate with a given file. The application  502  may be configured to instruct the file system which ID goes with the given file based, for example, on a determination that all of the data of the file may be deleted at the same time. In one embodiment, multiple erase blocks may be tagged with a particular stream ID. For example, using the device illustrated in  FIG. 5 , multiple erase blocks may be associated with Stream A, and data may be written directly to a given one of the erase blocks or striped across multiple pages associated with the erase blocks in Stream A. As another example, Stream B may comprise a single erase block, and data may be written to a given one of the pages or striped across multiple pages associated with the erase block associated with Stream B. The data associated with Stream A may have a different estimated deletion time than the data associated with Stream B. 
     The file system  504  may be configured to expose an application programming interface (API) to the application  502 . For example, the application  502 , via an API provided by the file system  504 , may be configured to tag a file with a particular stream ID. In addition, the application  502 , via an API provided by the file system  504 , may be configured to perform stream management, such as, for example, determining how many streams can be written to simultaneously, what stream IDs are available, and the ability to close a given stream. Further, the application  502 , via an API provided by the file system  504 , may be configured to determine a number of parameters associated with the stream such as, for example, the optimal write size associated with the stream. 
     The file system  504  may be further configured to intercept a write operation by the application  502  to a file in the device  508 , determine that the file is associated with a particular stream ID, and to tag the write operation (i.e.,  110  call) with the stream ID. The file system  504  may be further configured to store metadata associated with each file of the device  508 , and to further store the particular stream ID associated with each file along with the file metadata. 
     The storage driver  506  may be configured to expose an API to the file system  504 . For example, the file system  504 , via an API provided by the storage driver  506 , may be configured to enable stream functionality on the storage device  508 . The file system  504 , via an API provided by the storage driver  506 , may be further configured to discover existing streams on the device  508 . The file system  504 , via an API provided by the storage driver  506 , may be further configured to obtain information from the device such as, for example, the ability of the device to support streams and what streams, if any, are currently open on the device. The storage driver  506  may be configured to communicate with the device  508  and to expose protocol device agnostic interfaces to the file system  504  so that the storage driver  506  may communicate with the device  508  without the file system  504  knowing the details of the particular device. 
     The device  508  may comprise, for example, an SSD. The SSD illustrated in  FIG. 5 , for example, comprises eight erase blocks. Data may be written individually to a given erase block or may be striped across a plurality of the erase blocks in order to maximize throughput on the SSD. As also shown in  508 , and as further discussed herein, the plurality of erase blocks may be organized into streams such that data can be erased in a more efficient manner, as described above. For example, the SSD illustrated in  FIG. 5  comprises Stream A which is associated with three erase blocks and Stream B which is associated with a single erase block. 
     As discussed herein, streaming is a process by which data stored on an SSD may be grouped together in a stream comprising one or more erase blocks based, for example, on an estimated deletion time of all of the data in the stream. By storing data that is likely to be deleted together in the same erase block or group of erase blocks, numerous problems associated with SSD storage can be alleviated. However, the number of streams available on a given SSD may be limited. In some cases, the size of a given stream may be much larger than the amount data stored for a particular file, and assigning that to an individual stream may result in inefficient use of the streaming functionality offered by the SSD. Thus, it may be desirable to perform a combination of stream and non-stream writes for data associated with particular files based, for example, on the amount of data stored for the particular file and a size of each available stream block. 
     An example method for optimizing the use of streams available on a storage device is illustrated in  FIG. 6 . For example, the method may comprise writing data associated with a plurality of files to a first set of one or more erase blocks not associated with a stream, determining that an amount of data associated with a given one of the plurality of files in the first set of one or more erase blocks has reached a threshold, and moving the data associated with the given file from the first set of one or more erase blocks to a stream, the stream comprising a second set of one or more erase blocks different from the first set of one or more erase blocks. The first set of one or more erase blocks and the second set of one or more erase blocks may be located on a storage device, such as SSD  508  illustrated in  FIG. 5 .  FIGS. 7-11 , discussed below, illustrate in further detail the process of using both stream and non-stream writes to optimize the use of available streams. It is understood that the steps illustrated in  FIGS. 7-11  may be performed by any number of devices, including, for example, a file system associated with a computing device or the SSD comprising the one or more streams. 
       FIG. 7  illustrates a method of writing data associated with a plurality of files to a first set of one or more erase blocks on a storage device. As shown in  FIG. 7 , data associated with File A, File B and File C may be written to the first set of one or more erase blocks. The first set of one or more erase blocks may not be associated with a stream. A set of one or more erase blocks may comprise any number of erase blocks available on the storage device. In one example, the first set of one or more erase blocks may comprise all erase blocks on the storage device that are not associated with a stream. In another example, the first set of one or more erase blocks may comprise a subset of all erase blocks on the storage device that are not associated with a stream. In another example, the set of one or more erase blocks may comprise a single erase block. In another example, the first set of one or more erase blocks may comprise one or more erase blocks in a stream. As shown in the example of  FIG. 7 , data associated with File A, File B and File C may be written to erase block  1 . The set of one or more erase blocks may also comprise erase block  2  and erase block  3 . As also shown in the example of  FIG. 7 , erase block  4  may be associated with Stream  1  and erase block  5  may be associated with Stream  2 . However, as discussed herein, a stream may comprise any number of erase blocks. Data from each of File A, File B and File C may be written to any of erase blocks  1 ,  2  or  3  as part of a non-stream write. Thus, it is understood that data from each of File A, File B and File C may have a different estimated erase time. For example, it may be estimated that data associated with File A may be deleted two weeks from the time of the write operation, data associated with File B may be deleted two months from the time of the write operation and data associated with File C may be deleted two years from the time of the write operation. 
     As further shown in  FIG. 7 , a file system may be configured to keep track of the amount of data written for each file. For example, the file system may be configured to store metadata associated with each of the files. In one embodiment, the file system may be configured to maintain metadata about a file and its location on the storage device. For example, the metadata may take the form of a file extent mapping table, defining the offset, logical block address (LBA) and length of all data associated with a given file, as discussed further below. 
     As shown in  FIG. 8 , data associated with each of File A, File B and File C may be continuously written to the first set of one or more erase blocks. In one embodiment, as erase block  1  reaches capacity, data associated with each of the files may be written to erase block  2 . As data is continuously written for each of the files, it may be determined that an amount of data associated with a given one of the plurality of files in the first set of one or more erase blocks has reached a threshold. The threshold may be based on a storage capacity of one of more of the streams on the storage device. For example, a given stream may be able to store 256 MB of data. However, it is understood that the threshold may be based on any number of factors. For example, it could be possible that the application or some other entity residing on the computing device sends to the file system an indication that the file will soon be expanding in size and it would make sense to begin writing to a stream. In addition, metadata associated with the stream may define a threshold of, for example, 200 MB. The threshold may define the minimum amount of data that can be moved to the stream. Thus, when an amount of data associated with a given file in the first set of one or more erase blocks reaches 200 MB, data associated with the given file may be moved to a stream. It is understood that a stream may be of any size and that the threshold may be based on any number of metrics. It is further understood that a storage device may comprise multiple streams having different lengths, and that each of these streams may be associated with a different threshold. 
     As shown in  FIG. 9 , once this threshold is reached, data associated with the given file may be moved from the first set of one or more erase blocks to a stream. The stream may comprise a second set of one or more erase blocks different from the first set of one or more erase blocks. As discussed herein, the stream may be used exclusively to store data of the given file. For example, as shown in  FIG. 9 , all of the data associated with File A in the first set of one or more erase blocks may be moved to Stream  1 , Stream  1  being used exclusively to store data of File A. In the example that the first set of more erase are associated with a first stream, data may be moved from the first set of one or more erase blocks associated with the first stream to one or more erase blocks associated with a second stream, the first stream comprising data associated with a plurality of files and the second stream comprising data associated only with the given file. As also shown in  FIG. 9 , a trim operation may be performed on the data associated with the given file in the first set of one or more erase blocks. For example, a file system may be configured to instruct a storage device to execute a trim command on the data, thereby informing the storage device that the data inside the first set of one or more erase blocks is no longer in use and may be deleted. In response to receipt of the trim command, the storage device may be configured to “delete” the data associated with the given file in the first set of one or more erase blocks. As discussed herein, the storage device may need to perform garbage collection before the data can be permanently deleted. 
     As shown in  FIG. 10 , data associated with the given file may be written to the stream. For example, data associated with File A may be continued to be written to Stream  2  until the amount of data in the stream has reached a second threshold, as discussed further below. A size of the stream may be stored as metadata. As shown in the example of  FIG. 10 , an additional write operation for File A has been made to Stream  1 . As further shown in the example of  FIG. 10 , the amount of data in Stream  1  associated with File A may be approaching the capacity of the stream. 
     As shown in  FIG. 11 , in response to determining that the amount of data in the stream has reached a second threshold, the second threshold being based on a size of the stream, further data associated with the given file may again be written to the first set of one or more erase blocks. As shown in  FIG. 11 , the first set of one or more erase blocks may further comprise erase block  3  on the SSD. Erase block  3  may comprise, for example, data associated with File A and File C. However, it is understood that data may be written to any of the erase blocks on the storage device. For example, data associated with File A may be written to erase block  3  as well as any other available erase block on the SSD not associated with a stream. If at any point, data associated with a given one of the files has reached a predetermined threshold associated with an available stream on the storage device, the data may be moved to the stream comprising data exclusive to that file, as discussed herein. 
     In one example, the steps illustrated in  FIGS. 7-11  may be performed by a file system associated with a computing device. This method may be referred to herein as a “host managed” method. This example method, discussed further below, may comprise moving the data associated with the given file from the first set of one or more erase blocks to local memory, and then sending, to the storage device, a request to write the data associated with the given file from the local memory to a stream on the storage device. The file system may then update metadata that it maintains for the file to reflect the change in location of the data on the storage device. In another example, the steps illustrated in  FIGS. 7-11  may be performed by the storage device comprising the one or more streams. This method may be referred to herein as a “device managed” method. From the perspective of the storage device, this example method, discussed further below, may comprise receiving a stream identifier associated with the stream and a request to move the data associated with the given file from the first set of one or more erase blocks to the stream, copying the data associated with the given file from the first set of one or more erase blocks to the stream, and updating metadata maintained by the storage device to reflect the change in location of the data on the storage device. 
       FIG. 12  illustrates an example method implemented by a file system to optimize the use of available streams on a storage device. This method may be referred to as “host managed.” As shown at step  1202  of  FIG. 12 , a file system may be configured to determine that an amount of data associated with a given file in a first set of one or more erase blocks has reached a threshold, the first set of one or more erase blocks comprising data associated with a plurality of files. The file system may be, for example, file system  504  illustrated in  FIG. 5 . The storage device may be, for example, the SSD  508  illustrated in  FIG. 5 . As discussed above in connection with  FIGS. 7-11 , data associated with a plurality of files may be written to the first set of one or more erase blocks. The first set of one or more erase blocks may correspond, for example, to a first erase block and a second erase block. The threshold may be based on a storage capacity of the one or more available streams on the storage device. For example, the file system  504  may determine that when data associated with the given file in the first set of one or more erase blocks reaches half of the maximum storage capacity of a given stream, to move the data associated with that file to the available stream. As discussed further below, the size of the stream may be stored as metadata. 
     As shown at step  1204  of  FIG. 12 , the file system  504  may be configured to write the data associated with the given file to memory. The memory may be, for example, system memory  116  associated with computing device  112  illustrated in  FIG. 1 . 
     As shown at step  1206  of  FIG. 12 , the file system  504  may be configured to send, to the storage device  508 , a request for a stream identifier, the stream identifier being associated with a stream. The stream may comprise a second set of one or more erase blocks different from the first set of one or more erase blocks. For example, as illustrated in  FIG. 9 , the stream may comprise a single erase block, such as erase block  4 . However, it is understood that a stream any comprise any number of erase blocks on the storage device  508 . 
     As shown at step  1208  of  FIG. 12 , the file system  504  may receive, from the storage device  508 , the stream identifier. The storage device  508  may be configured to determine an available stream based, for example, on the amount of data associated with the file to be stored in the stream, and to send to the file system  504  the stream identifier associated with that stream. Receiving the stream identifier from the storage device  508  may grant exclusive access to the stream by File A. 
     As shown at step  1210  of  FIG. 12 , the file system  504  may send, to the storage device  508 , a request to write the data associated with the given file from the local memory to the stream. As shown at  FIG. 9 , the stream may comprise data exclusive to the given file. Sending the request to write the data associated with the given file to the stream may comprise sending, to the storage device  508 , the stream identifier associated with the stream. Sending the stream identifier may instruct the storage device  508  where to write the data associated with the given file. 
     As further shown in  FIG. 9 , the file system  504  may be further configured to instruct the storage device  508  to execute a trim command on the data associated with the given file in the first set of one or more erase blocks. The trim command may inform the storage device  508  that the data inside the first set of one or more erase blocks is no longer in use and may be deleted. In response to receipt of the trim command, the storage device  508  may be configured to delete the data associated with the given file in the first set of one or more erase blocks. As discussed above, the storage device  508  may need to perform garbage collection before the data can be permanently deleted. 
     As discussed above, the file system  504  may maintain metadata for each file that keeps track of the location(s) of the data associated with the given file on the storage medium. This metadata may take the form of, for example, a file extent table, as shown in  FIGS. 7-11 . The file extent table may define, for example, an offset, a logical block address (LBA), and a length of each data range of a given file stored on the storage device. In the example of  FIG. 7 , the file extent table comprises data for File A. However, it is understood that the file extent table may comprise data for any number of files. Each data entry for a given file in the erase block may correspond to a page of data, such as one of pages  208  illustrated in  FIG. 2 . As discussed above in connection with  FIG. 2 , a page may be the smallest unit of the SSD  508  that can be programmed. As shown in the table of  FIG. 7 , two pages of data may be written to erase block  1 , the pages beginning at LBA  0  and having an offset of 2. An offset may refer to the number of pages of data associated with the given file at the time of the write operation, while the length may refer to the number of consecutive pages associated with the file. As further shown in  FIG. 7 , a third page of data associated with File A may be written to erase block  1 , the third page of data beginning at LBA  3  with an offset of 2. As shown in  FIG. 8 , additional write operations may be performed to the first set of one or more erase blocks. For example, a single page of data associated with File A may begin at LBA  8 , two pages of data associated with File A may begin at LBA  10 , and two pages of data associated with File A may begin at LBA  14 . 
     As discussed herein, when the file system  504  determines that a threshold amount of data associated with a given file has been met, the file system may move the data from the first set of one or more erase blocks to a stream. Once the write operation is completed, the file system may update the metadata it stores for the file to reflect the change in location of the data of file A. For example, in an embodiment in which the file metadata takes the form of one or more entries in a file extents table that map byte offsets of ranges of data of the file to logical block addresses (LBA) associated with the locations of those ranges on the storage device, the LBAs for the file may be updated to reflect the new location of the data in the stream on the storage device. For example, as shown in  FIG. 9 , each of the pages of data associated with File A has been moved to Stream  1 . Thus, the file extent table may be updated to reflect the new LBA for the ranges of data associated with File A in Stream  1 . Because the ranges of data have been moved to consecutive logical addresses on the storage device in Stream  1 , a single entry suffices to indicate that the data, having a length of “8” now resides starting at LBA “30” of the storage device. 
     As shown in  FIG. 10 , as additional write operations are made to File A, the file extent table may be updated to include the additional pages of data. For example, as one page of data is added to Stream  1 , the file extent table may be updated to include information about the location of that additional page of data associated with File A. As shown in  FIG. 11 , as the threshold of Stream  1  has been reached and no new data can be written to the stream, data associated with File A may be written to another location on the storage device, such as, for example, the first set erase blocks not associated with a stream. Thus, the file extent table may be further updated to include those new entries. In the example of  FIG. 11 , two new pages of data associated with File A have been written to the first set of one or more erase blocks, a first page beginning at LBA  20  and a second page beginning at LBA  22 . 
       FIG. 13  illustrates a method performed by a storage device, such as SSD  508  illustrated in  FIG. 5 , to optimize the use of available streams on the storage device. This example may be referred to a “device managed.” For example, as shown at step  1302  of  FIG. 13 , the storage device  508  may be configured to receive, from a file system, a request for a stream identifier, the file system being configured to send to the storage device the request for the stream identifier in response to a determination at the file system that data associated with a given file in a first set of one or more erase blocks on a storage device has reached a threshold, the first set of one or more erase blocks comprising data associated with a plurality of files. The file system may be, for example, file system  504  illustrated in  FIG. 5 . The file system  504  may make a determination that the data associated with a given file in a first set of one or more erase blocks has reached a threshold based on metadata stored in the file system. As one example, the metadata may comprise a size of the stream. 
     As shown at step  1304  of  FIG. 13 , the storage device  508  may send, to the file system  5 - 4 , the stream identifier. The stream identifier may be associated with a stream comprising a second set of one or more erase blocks on the storage device  508  different from the first set of one or more erase blocks. 
     As shown at step  1306  of  FIG. 13 , the storage device  508  may receive, from the file system  5 - 4 , a request to copy data associated with the given file from the first set of one or more erase blocks to the stream. The request may include the stream identifier associated with the stream. As shown in the example of  FIG. 9 , all data associated with File A may be moved from erase blocks  1  and  2  to Stream  1 . Receiving a request to copy data associated with the given file from the first set of one or more erase blocks to the stream may comprise receiving, from the file system  504 , a logical block address of the data associated with the given file. In one embodiment, the storage device  508  may further be configured to update metadata in the storage device  508  to include a location of the data associated with the given file in the stream. The location may comprise a physical block address of the data associated with the given file in the stream. For example, the storage device  508  may maintain a LBA to physical block mapping table, and upon receiving the LBAs of the data associated with the given file and copying the data associated with the given file from the first set of one or more erase blocks to the stream, may update the LBA to physical block mapping table to include a new physical block address(es) of the data associated with the given file. Having the storage device update its mapping of LBAs to physical blocks alleviates the need for the file system to update its own metadata (e.g., file extents table); hence the use of the term “device managed” to describe this embodiment. 
     As shown at step  1308 , the storage device  508  may be configured to copy the data associated with the given file from the first set of one or more erase blocks to the stream. As shown in  FIG. 9 , the storage device  508  may be further configured to execute a trim command on the data associated with the given file in the first set of one or more erase blocks. As discussed above, there may be less overhead associated with the example method performed by the storage device, as the file system may not need to update its file location metadata (e.g., file extent mapping table). Instead, the storage device may update the physical addresses associated with each LBA range, while maintaining the same LBAs from the viewpoint of the file system. 
     The illustrations of the aspects described herein are intended to provide a general understanding of the structure of the various aspects. The illustrations are not intended to serve as a complete description of all of the elements and features of apparatus and systems that utilize the structures or methods described herein. Many other aspects may be apparent to those of skill in the art upon reviewing the disclosure. Other aspects may be utilized and derived from the disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive. 
     The various illustrative logical blocks, configurations, modules, and method steps or instructions described in connection with the aspects disclosed herein may be implemented as electronic hardware or computer software. Various illustrative components, blocks, configurations, modules, or steps have been described generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality may be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. 
     The various illustrative logical blocks, configurations, modules, and method steps or instructions described in connection with the aspects disclosed herein, or certain aspects or portions thereof, may be embodied in the form of computer executable instructions (i.e., program code) stored on a computer-readable storage medium which instructions, when executed by a machine, such as a computing device, perform and/or implement the systems, methods and processes described herein. Specifically, any of the steps, operations or functions described above may be implemented in the form of such computer executable instructions. Computer readable storage media include both volatile and nonvolatile, removable and non-removable media implemented in any non-transitory (i.e., tangible or physical) method or technology for storage of information, but such computer readable storage media do not include signals. Computer readable storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other tangible or physical medium which may be used to store the desired information and which may be accessed by a computer. 
     Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims. 
     The description of the aspects is provided to enable the making or use of the aspects. Various modifications to these aspects will be readily apparent, and the generic principles defined herein may be applied to other aspects without departing from the scope of the disclosure. Thus, the present disclosure is not intended to be limited to the aspects shown herein but is to be accorded the widest scope possible consistent with the principles and novel features as defined by the following claims.