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As you can see, the SSD DC S3700 offers good performance in random 4 KB reads and writes. Both capacities achieve their specifications or slightly exceed them at reasonably-low queue depths. You won't see the performance levels of a desktop drive based on a second-gen SandForce controller (a theme you'll see throughout our tests), but this still represents a significant step up from Intel's previous generation of enterprise-oriented SSDs.
Indeed, Intel claims to trade best-in-class throughput for consistency and low latency. Let's have a look at the latency tied to these results to gauge the true impact of the company's optimizations.
The SSD DC S3700 behaves more like a PCI Express-based drive, such as Micron's P320h or OCZ's Z-Drive R4, than its peers in the SATA-based space. In fact, we measure average and maximum response times that are lower than Intel's SSD 910 (1.62 and 41.77 ms, respectively).
Comparing these numbers to Intel's QoS specification, the 800 GB model is well within the 20 ms maximum time allowed for 99.9999% of round-trip writes. However, the 200 GB drive is slightly higher than the spec, at 26.21 ms. Is there a plausible explanation for this anomaly?
It's likely attributable to the passing of time. We make the drives that go through our enterprise storage review process suffer quite a bit as we generate results. In some cases, the tests take hours. Other times, they take days. Our random 4 KB write testing, which was used to generate our latency numbers, involved 24 hours of testing. We do this to more definitively address issues that might not surface during shorter tests. And if you're buying enterprise-class hardware, you want the guys reviewing those drives to be thorough. So, when we look back at our data and do a little bit of math, it's easy to see why the 99.9999th percentile still leaves a lot of commands that theoretically could take longer.
In this case, we have roughly 30,000 IOPS x 86,400 seconds, or roughly 2.5 billion operations. That leaves 2,500 operations outside of Intel's specification. We went back and reran the tests on the both the 200 and 800 GB drives and saw similar results, where just a handful (roughly 0.0001%) of commands were outside of the spec. More surprising was that nearly 99.995% of writes fell below 10 ms, which is significantly better than Intel's reference.