SNIA IOPS TESTING
The Storage Networking Industry Association has an entire industry accepted performance test specification for solid state storage devices. Some of the tests are complicated to perform, but they allow us to look at some important performance metrics in a standard, objective way.
SNIA’s Performance Test Specification (PTS) includes IOPS testing, but it is much more comprehensive than just running 4KB writes with IOMeter. SNIA testing is more like a marathon than a sprint. In total, there are 25 rounds of tests, each lasting 56 minutes. Each round consists of 8 different block sizes (512 bytes through 1MB) and 7 different access patterns (100% reads to 100% writes). After 25 rounds are finished (just a bit longer than 23 hours), we record the average performance of 4 rounds after we enter steady state.
- Preconditioning: 3x capacity fill with 128K sequential writes
- Each round is composed of .5K, 4K, 8K, 16K, 32K, 64K, 128K, and 1MB accesses
- Each access size is run at 100%, 95%, 65%, 50%, 35%, 5%, and 0% Read/Write Mixes, each for one minute.
- The test is composed of 25 rounds (one round takes 56 minutes, 25 rounds = 1,400 minutes)
What stood out when we compared the SNIA results for the S3500 and SM843 was the 65% and 95% reads at 512B and 4KB. In each case, the S3500 had a 50% advantage over the SM843. This is especially odd considering the SM843 posted better 100% read results at all transfer sizes. This follows the trend was saw with the average response times. The S3500 just performs better with a lightly mixed workload.
Unlike our other performance tests, the SNIA tests only last for a relatively short period of time each (1 minute), but they cover many more access patterns and transfer sizes. You may have noticed that some of the SNIA results are higher or lower than in our other tests. The reason for this is because SSD performance is heavily predicated on previous workloads. Toggling between large and small blocks and reads to writes is stressful on the drive and results can vary. This is why we take the average of multiple runs. What it does show is how well a drive’s firmware can perform garbage collection, TRIM and many other internal housekeeping tasks.