Spec released Enterprise SSD test

The Storage Networking Industry Association (SNIA) today announced the release of a specification that can be used to test the performance of solid state drives, regardless of vendor.SNIA, a group of trade industry vendors and universities which develops and promotes standards for storage systems, said its (SSSI) solid state storage Initiative came with the specification of Performance SSD Test for equality of opportunity in reference tests.The SSSI publishes two versions of the specification of test: this week for enterprise SSDs and another server or on the side of client SSDs, which will be published in the third quarter of this year.The Test of Performance of Enterprise specification (PDF document) defines a set of tests of peripheral level and methodologies to enable controlled trials of devices SSD in enterprise systems, such as storage arrays. Previously, no there was no testing methodology widely accepted for measuring the performance of the SSD device. Each SSD manufacturer used different measuring methods for deriving specifications for performance for their products.

"You could not compare a data sheet to another sheet of data and expect to understand if a disk was faster than the other because the factory used different settings, said Paul Wassenberg, Chairman of the Board of Directors SSSI." Today, the SSD market is from where the hard disk market was in the 1970s. "There are many from different vendors that offer products with a lot of different abilities and there are a lot of variability."More than 40 companies spent two years in development of Performance Test Specification (PTS), said Wassenberg. Among these companies were all the major manufacturers of DSS and storage system, including Samsung, Intel, Marvell, Toshiba, IBM, Seagate, Dell, EMC, Hitachi Data Systems and Western Digital.Jim Handy, an analyst with the research Objective analysis firm which was the work of the technical specification group, said: "test SNIA specification is not an alpha, but it is certainly a major step in front of the specificatons which are commonly used by SSD manufacturers."Handy said one of the most important aspects of the specification is that it is prudent to ensure that the SSD is first "preconditioning" before testing, sense data are first written to them and then deleted to break the readers.

All SSDs slow after initial use because once a sufficient amount of data has been written for them, the processor in the drive starts to move data in a process called read-modify-erase-write cycle. Simply put, when a DSS is a new, data can be written to it without interference from management software. However, once the reader has been a certain amount of data written to, the NAND flash memory used in the manufacture of SSDs requires that old data first marked for deletion before new data memory. Then, once the new data is written, the blocks of old marked for deletion are actually removed in a process called garbage collection."

SNIA has created a set of nomenclatures used to describe the life cycle of an SSD. A new hard disk SSD is called FOB, of "fresh out of the box". After initial use of an SSD, it falls in a scene that terms SNIA steady, when State of performance levels and can be measured with precision. "In terms of performance, reads are faster, entries are slower and clears is slower," said Wassenberg.

Handy and Tom Coughlin, Coughlin Associates consultancy, in collaboration with Calypso to compile a study on the performance of SSD founder involved 18 different readers. "We found that there was no consistency in performance between the two SSDs". "They vary throughout the map," Handy said, adding that some cells only level SSDs (SLC) worse than less expensive SSDs out multi-level cell (MLC).

"And some MLC-based SSDs are slower than a hard-drives business once they are entered into their steady state," Handy said. Handy and Coughlin tested 18 readers using the PTS specification. No two was similar.How long it takes an SSD to move in a State of equilibrium which is reliable for testing varies from a product, but the new specification requires that a DSS go through five distinct performance tests before being compared."The essential with the PTS specification is that it tells you what to do and how to prepare the drive." It is the only way to test the performance? No.. But, over time, we found it very effective and the most reliable way. "You can run the test several times and get the same result," said Wassenberg.

Test FTP sequence is as follows:

Purge: set SSD in condition FOB close by independent dataWorkload prerequisite erasure: write required data for any DSS to facilitate reaching based stable StateWorkload prerequisite: run the Test loop itself until the DSS is in constant StateTest: take action when DSS is in steady state The STP describes a reference material and software test platform used to validate the specification itself. The reference test platform was developed by Member of the systems Calypso SSSI. Calypso built a hardware platform that several bays for test drives in parallel and developed the software that adheres to the specification."You pretty much Plug-and-in a reader, and this is the test", said Wassenberg. "If you want to test a drive, they'll test it for a fee." "This reference test platform is the gold standard."But said Wassenberg users can put in place their own testbed with the spec and other open source of benchmarking tools such as DBench or Iometer. "You must just ensure that you use a hardware platform that is bottleneck DSS." "We recommend a motherboard server,", he said. "You must be savvy enough to write [a] script for it.".

The SNIA is currently also working on the specifications to the application that will allow the SSDs to test under loads for specific tasks. For example, SSDs could be tested for their performance in environments PC running Windows 7 or in environments of software Oracle server. "But this is way off the coast." "The important thing for us was to get something out there to test the disks with and compare performance", said Wassenberg.

[Lucas Mearian covers storage, recovery and continuity of disaster Affairs, infrastructure, financial services and health care IT Computerworld.] Follow Lucas on Twitter at @ lucasmearian or subscribe flow RSS of Lucas. [Email address is lmearian@computerworld.com.]


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