JEDEC JESD219A-2012 Solid-State Drive (SSD) Endurance Workloads.pdf

1、JEDEC STANDARD Solid-State Drive (SSD) Endurance Workloads JESD219A (Revision of JESD219, September 2010) JULY 2012 JEDEC SOLID STATE TECHNOLOGY ASSOCIATION NOTICE JEDEC standards and publications contain material that has been prepared, reviewed, and approved through the JEDEC Board of Directors le

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9、3 North 10th Street Suite 240 South Arlington, VA 22201-2107 or refer to www.jedec.org under Standards-Documents/Copyright Information. JEDEC Standard No. 219A Page 1 SOLID STATE DRIVE (SSD) ENDURANCE WORKLOADS (From JEDEC Board Ballot, JCB-12-16, formulated under the cognizance of the JC-64.8 Subco

10、mmittee on Solid-State Drives.) 1 Scope This standard defines workloads for the endurance rating and endurance verification of SSD application classes. These workloads shall be used in conjunction with the Solid State Drive (SSD) Requirements and Endurance Test Method standard, JESD218. 2 Reference

11、documents JESD218, Solid State Drive (SSD) Requirements and Endurance Test Method 3 Terms and definitions cluster: The minimum # of contiguous LBAs allocated by the host operating system. Cold LBA Range: An LBA Range not referenced by a write or trim in a trace. command trace: A trace of I/O command

12、s. compression: The process of scaling LBAs associated with commands in the Master Trace to produce a Test Trace with a smaller LBA Range. entropy: The non-compressibility of a data pattern when in file format such that 100% entropy has no reduction in file size and 50% entropy has approximately a 5

13、0% reduction in file size when converting to a zip file. expansion: The process of scaling LBAs associated with commands in the Master Trace to produce a Test Trace with a larger LBA Range. footprint: A set of LBAs. Free LBA Space: A set of LBAs within LBA Address Space, which are not currently allo

14、cated for data storage by the host OS. LBA Address Space: The full set of user addressable LBAs on the device. LBA Range: The set of contiguous LBA addresses bounded by the lowest and highest LBA of an addressed structure. Maximum LBA: A value specifying the LBA number corresponding to the last LBA

15、in the LBA Address Space. Master Trace: A command trace typical of a period of continuous drive operation in a typical client environment, from which Test Traces are derived. JEDEC Standard No. 219 Page 2 3 Terms and definitions (contd) PreCond%full: The % of clusters in LBA Address Space that are a

16、ssigned to valid data on the device under test by the preconditioning process. SSD_Capacity: See JESD218. Test Trace: A command trace comprising I/O operations to a drive under test that is run during the test phase of a client workload. Trim: A command from the host that identifies data that is no

17、longer used by the operating system, allowing the memory space to be considered Free LBA Space by the drive. 4 Enterprise endurance workload The enterprise endurance workload consists of random data distributed across an SSD in a manner similar to some enterprise workload traces that are publicly av

18、ailable for review. Prior to running the workload, the SSD under test shall have the user-addressable LBA space filled with valid data (e.g., the drive does not return a data read error because of the content of the LBA prior to being written during the test routine). Initialization may not be neces

19、sary if the formatted SSD satisfies this requirement. a) The enterprise endurance workload shall be comprised of random data with the following payload size distribution: 512 bytes (0.5K) 4% 1024 bytes (1K) 1% 1536 bytes (1.5K) 1% 2048 bytes (2K) 1% 2560 bytes (2.5K) 1% 3072 bytes (3K) 1% 3584 bytes

20、 (3.5K) 1% 4096 bytes (4K) 67% 8192 bytes (8K) 10% 16,384 bytes (16K) 7% 32,768 bytes (32K) 3% 65,536 bytes (64K) 3% b) The data payloads greater than or equal to 4096 bytes data payload sizes shall be arranged such that the data payloads less than 4096 bytes are pseudo randomized among the data pay

21、loads greater than or equal to 4096 bytes. Data payloads greater than or equal to 4096 bytes are aligned on 4K boundaries. JEDEC Standard No. 219A Page 3 4 Enterprise endurance workload (contd) c) The workload shall be distributed across the SSD such that the following is achieved: 1) 50% of accesse

22、s to first 5% of user LBA space (LBA group a) 2) 30% of accesses to next 15% of user LBA space (LBA group b) 3) 20% of accesses to remainder of user LBA space (LBA group c) d) To avoid testing only a particular area of the SSD, the distribution described in c) is offset through the user LBA space on

23、 different units under test such that all of the SSD LBAs are subjected to the highest number of accesses (e.g., SSD 1 has LBA group a applied to the first 5% of LBAs, SSD 2 has LBA group a applied to the next 5% of LBAs, etc). e) The write data payload size distribution shall be applied to each of

24、the three LBA groups concurrently. The write sequence across the LBA groups may be applied in either a deterministic fashion or randomly, depending on the capabilities of the test tools, so long as the percentage of accesses to each LBA group conforms to those specified in 4c and the LBA access shal

25、l be random (not sequential) within each LBA group. An example of a deterministic method is given in Annex A.1 and an example of a random method is given in Annex A.2. f) Random data is considered to have 100% entropy. The randomization of the data shall be such that if data compression/reduction is

26、 done by the SSD under test, the compression/reduction has the same effect as it would on encrypted data. It is acceptable to substitute a few bytes in each sector with metadata (such as the LBA number) or other information in place of the random data in those bytes if the addition of such informati

27、on provides enhanced test interpretation capability. The random data for the payload may be generated by various means. An informative example script for generating the random data and the read/write distribution across LBA groups is provided in Annex A.2. This script uses open-source software that

28、may be found at vdbench.org. 5 Client endurance workload 5.1 Client endurance workload overview The client endurance workload consists of a standard reference trace of standard ATA I/O commands, played back on the target device. The standard TBW rating for a client drive shall be derived for and ver

29、ified under the following workload conditions: a) PreCond%full = 100%; b) trim commands enabled; and c) random data pattern. Additional TBW ratings may optionally be derived and verified for different values of these parameters; however, such ratings shall be reported only in addition to the standar

30、d TBW rating. See clause 6 concerning extrapolation of non-standard TBW ratings. JEDEC Standard No. 219 Page 4 5.1 Client endurance workload overview (contd) The application of the client workload occurs in two phases: 1. Preconditioning Phase The preconditioning phase establishes an initial pattern

31、 of free LBA distribution within the LBA Address Space of the drive under test. This phase creates the logical fullness of the drive at the start of the test phase, as defined by the PreCond%full parameter specified for the test. The preconditioning phase comprises the following two steps. 1) Write

32、once, sequentially, to the full LBA Address Space using random data (see 5.3.2). If additional TBW ratings are being determined with non-random data (see 5.3.3), non-random data shall be used for this step instead of random data. 2) Create Free LBA Space from the Maximum LBA contiguous to the lower

33、LBA address corresponding to the PreCond%full value if the PreCond%full value is less than 100%. 2. Test Phase The test phase stresses the drive in a manner that is representative of use during long-term operation in a client environment. The test phase comprises multiple runs of a Test Trace. The T

34、est Trace has the same LBA footprint for each iteration. During the test phase, a Test Trace, as specified in 5.2.2, is run repeatedly, per the methods specified in JESD218. The client endurance workload traces referenced in this standard are contained in a trace library maintained by JEDEC and can

35、be downloaded at www.jedec.org, using search criteria: JESD219. 5.2 Client Endurance Workload Traces 5.2.1 Master Trace A Master Trace is a command trace from which all Test Traces within the SSD_Capacity range of the Master Trace in the trace library are derived. It comprises drive input/output ope

36、rations captured over extended period of time in a single user PC with an installed operating system that supports trim commands. The Master Trace incorporates all I/O operations to a representative SSD, including those occurring during shutdown/boot and hibernate/restore activity. Operations includ

37、e the following: a) write commands; b) trim commands1c) flush cache commands. ; This Master Trace should not be used to verify the endurance of SSDs utilized in cache applications since the workload may vary from the activity performed in the client workload Master Trace. 1JESD219 refers to trim com

38、mands. Trim applies to the ATA command set. The equivalent of the trim command is defined in other interface standards (e.g., SCSI Unmap; NVMe Deallocate). If a device using a command set other than ATA is being tested, the relevant form of trim for the devices command set should be used by the test

39、 software. JEDEC Standard No. 219A Page 5 5.2.1 Master Trace (contd) A Master Trace may be scaled to produce Test Traces for use with a drive of any capacity within the SSD_Capacity range of the Master Trace by means of compression or expansion. Compression or expansion is used to create a Test Trac

40、e with an LBA Range that almost spans the LBA address range of the drive to which it relates. Compression is achieved by reducing the length of Cold LBA Ranges in the trace. Expansion is achieved by increasing the length of Cold LBA Ranges in the trace. Cold LBA RangeCompressedCold LBA RangeWrite/Tr

41、im LBA Range1 2 3 4 51 2 3 4 5LBA Footprint ofMaster TraceCompressedLBA Footprint forTest Trace1 2 3 4 5ExpandedLBA Footprint forTest TraceExpandedCold LBA RangeFigure 1 Compression and Expansion of Master Trace If the Master Trace has an LBA Range = M, and it is required to create a Test Trace with

42、 LBA Range = T, then the total length of Cold LBA Ranges within the Master Trace is compressed (or expanded) by M-T in order to create the Test Trace. If the total length of all the Cold LBA Ranges within the Master Trace is C, then the length of each individual Cold LBA Range, of length 20MB, shall

43、 be reduced by a fraction (M-T)/C, or increased by a fraction (T-M)/C, as appropriate. During reduction or expansion, the change in length of an individual Cold LBA Range should be a multiple of 4KB. 5.2.2 Test Trace A Test Trace contains all commands that are present in the Master Trace. The LBA Ra

44、nge of a Test Trace almost spans the LBA address range of the drive to which it relates. A Test Trace for a specified SSD_Capacity parameter is derived from the Master Trace with the use of compression or expansion if required. The Test Trace may combine consecutive trim commands found in the Master

45、 Trace into a single trim command. Multiple Test Traces exist in the JEDEC trace library, each corresponding to a specific value of the SSD_Capacity parameter. JEDEC Standard No. 219 Page 6 5.3 Client workload data patterns 5.3.1 Data pattern overview The workload trace files only contain the ATA I/

46、O commands. The data payload content of the LBAs is not included in the traces due to the size of such a file not being practical and due to the need for the data to change within the LBA during repeated writes. Some drives may include data compression or reduction techniques. Some encryption softwa

47、re may cause data to become essentially 100% random. Due to these variables, random data shall be used as the standard TBW rating condition. Based on examination of drives in field applications, for additional TBW ratings of drives that incorporate data compression or reduction techniques, the non-r

48、andom data shall have entropy of approximately 50%. 5.3.2 Random data Random data shall be generated according to the description for the enterprise workload (see 4f). A local copy of the test trace file may be written to the SSD in place of some random data as required by the testing method. 5.3.3

49、Non-random data Non-random data patterns should be created using the non-random data file created by the Perl code located in Annex B.1. The non-random data file generated by this Perl code has approximately 50% entropy. A random byte offset shall be used to ensure that the data selected from the non-random data file has sufficient randomness to exceed the SSD_Capacity. It is acceptable to substitute a few bytes in each sector with metadata (such as the LBA number) or other information in place of the non-random data in those bytes if the addition of such information provides