26 April 2011

Download Solid State Storage (SSS) Performance Test Specification (PTS) Enterprise

Purpose

Manufacturers need to set, and customers need to compare, the performance of Solid State Storage (SSS) devices. This Specification defines a set of device level tests and methodologies intended to enable comparative testing of SSS devices in Enterprise (see 2.1.4) systems.

Background

A successful device level performance test isolates the device being tested from the underlying test platform (HW, OS, Tools, Applications) so the only limiting variable in the test environment is the device being tested. To achieve this goal with NAND-based SSS devices, in addition to typical system/device isolation issues, the test, and test methodologies, must address attributes unique to NAND-based flash media.

NAND-based SSS device controllers map Logical to Physical blocks on the NAND media, in order to achieve the best NAND performance and endurance. The SSS device manages this LBA-to-PBA mapping with internal processes that operate independently of the host. The sum of this activity is referred to as “flash management”.

The performance of the flash management during a test, and hence the overall performance of the SSS device during the test, depends critically on:

1. Write History and Preconditioning: The state of the device prior to the test
2. Workload Pattern: Pattern of the I/O (r/w mix, block size, etc.) written to device during test
3. Data Pattern: The actual bits in the data payload written to the device

The methodologies defined in the SSS Performance Test Specification (SSS PTS) attempt to create consistent conditions for items 1-3 so that the only variable is the device under test.

The importance of the SSS PTS methodologies on SSS performance measurement is shown in Figure 1-1. A typical SSS device, taken Fresh Out of the Box (FOB), and exposed to a workload, experiences a brief period of elevated performance, followed by a transition to Steady State performance. The SSS PTS ensures that performance measurements are taken in the Steady State region, representing the device’s performance during its normal working life.