IOPS (I/Os per Second) Test


The IOPS test measures the random IO performance covering a broad range of R/W (Read/Write) and Block Size combinations of interest to most users.  7 R/W mixes ranging from 100% Read to 100% Write, and 8 Block Sizes ranging from 0.5KiB to 1024 KiB are used.  Using the table and/or the 2D and 3D plots provided in the SNIA Report template, the user can quickly retrieve the performance values of interest.

Test Setup:

The general IOPS test sequence is: 

  1. PURGE the device.
  2. Perform the necessary Workload Independent Preconditioning (WIPC).  Note that depending on whether the test is PTS-E (PTS Enterprise) or PTS-C (PTS Client), this WIPC may include both sequential and random preconditioning.
  3. Perform Workload Dependent Preconditioning (WDPC), which is also the actual test stimulus, until Steady State Criteria as set forth in the Specification is reached.  The Steady State Criteria calls for maximum data excursion and maximum slope excursion to be within a 20% and 10% of the average, respectively.

Note that the Steady State Measurement Window (the portion of data that is used to determine conformance to Steady State) is made up of 5 “Rounds”.  A “Round” is defined by a single sweep through the 56 element Block Size x R/W mix matrix (8 Block Sizes: 0.5, 4, 8, 16, 32, 64, 128 and 1024 KiB and 7 R/W Mixes: 0/100, 5/95, 35/65, 50/50, 65/35, 95/5 and 100/0).  Each Block Size R/W combination is tested for one minute resulting in a single Round test time of 56 minutes.

Benefits of IOPS Test:

  1. Provides Critical Steady State Values:  Key to the SNIA test specification is the emphasis on “Steady State Results”.   This test shows how the device will perform UNDER STEADY STATE CONDITIONS.    Many of the “Up to xxxx IOPS” specifications provided on box-tops usually are transient and not observed under sustained loads, or require special conditions for the performance to hold true. 
  2. Covers Broad Range of R/W and Block Size:  Users can simply refer to the table to obtain the R/W-Block Size value of interest.  For example, Online Transaction Processing applications typically run at Block Size=8 KiB, R/W Mix=65/35.  Users can quickly understand how the device might perform under Steady State at these access characteristics.

IOPS vs R/W & Block Size Charts Give Good Overview:  The 2D and 3D charts provided in the SNIA report template provide an at-a-glance view of the drive’s overall performance.  In particular, the user can easily identify regions that relate to read/write performance parity as well as small to large block performance differences.