Random Performance – Iometer (IOPS/latency), YAPT (random)

We are trying something different here. Folks tend to not like to click through pages and pages of benchmarks, so I'm going to weed out those that show little to no delta across different units (PCMark). I'm also going to group results performance trait tested. Here are the random access results:


Iometer is an I/O subsystem measurement and characterization tool for single and clustered systems. It was originally developed by the Intel Corporation and announced at the Intel Developers Forum (IDF) on February 17, 1998 – since then it got wide spread within the industry. Intel later discontinued work on Iometer and passed it onto the Open Source Development Lab (OSDL). In November 2001, code was dropped on SourceForge.net. Since the relaunch in February 2003, the project is driven by an international group of individuals who are continuesly improving, porting and extend the product.

Iometer – IOPS

The cap at ~200k in this test is actually a limit of our Iometer configuration (pegging a CPU core). Back when we tested the SSD 750, I figured that would be the only SSD to reach that limit on a single IOPS-driving thread. I was mistaken. While it doesn't beat the SSD 750 at any single metric, the NVMe SM951 is certainly nipping at the 750's heels. Another interesting point of note was that the AHCI SM951 actually beat out its NVMe counterpart in a few tests at very low queue depths. This may have been partially due to there being more flash dies available (the AHCI part was 2x the capacity), combined with a higher write speed rating on the AHCI part. Our Web Server test is pure reads, and we see both variants track more as we might expect (NVMe > AHCI). This is more apparent and clearly visible in the latency results below.

Iometer – Average Transaction Time

For SSD reviews, HDD results are removed here as they throw the scale too far to tell any meaningful difference in the results. Queue depth has been reduced to 8 to further clarify the results (especially as typical consumer workloads rarely exceed QD=8). Some notes for interpreting results:

  • Times measured at QD=1 can double as a value of seek time (in HDD terms, that is).
  • A 'flatter' line means that drive will scale better and ramp up its IOPS when hit with multiple requests simultaneously, especially if that line falls lower than competing units.

Some great low latencies seen here. Not as low as the SSD 750, but still great for such a small form factor product.

YAPT (random)

YAPT (yet another performance test) is a benchmark recommended by a pair of drive manufacturers and was incredibly difficult to locate as it hasn't been updated or used in quite some time.  That doesn't make it irrelevant by any means though, as the benchmark is quite useful.  It creates a test file of about 100 MB in size and runs both random and sequential read and write tests with it while changing the data I/O size in the process.  The misaligned nature of this test exposes the read-modify-write performance of SSDs and Advanced Format HDDs.

This test has no regard for 4k alignment, and it brings many SSDs to their knees rather quickly. The SSD 750 is heavily optimized for 4k aligned writes, which explains those inconsistent results. The SM951's don't seem to care in the least about that little issue, and turn in results that are more in line with their maximum sequential write ratings. Note that the NVMe SM951 is rated at a lower write speed than the AHCI version.

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