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Results: Performance Consistency

SanDisk Optimus Eco SSD: A SAS Interface And Up To 2 TB Of Flash
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Increasingly, we pay close attention to the performance consistency of enterprise-class SSDs. This is what separates a good drive from a great one when all of the corner case testing seems equal. Over the past year, we measured this in terms of large block transfers in our Enterprise Video Streaming section. Armed with this data and our exclusive analysis, the peaks, valleys, and frequency of each become clear. If you look at the information for long enough, you start to see fingerprints for each drive.

We start with large-block transfers because, in enterprise video applications, if you don't buffer or write data fast enough, you can lose it completely. Random 4 KB transfers are slightly more academic, but they also match database transfers more closely. With this sort of workload, you might not lose data, but the system will slow down.

For the following tests, we subject SanDisk's Optimus Eco and Intel's SSD DC S3700 to 25 hours of continuous random 4 KB writes across each drive. We record IOPS every second, giving us 90,000 data points. We then zoom in to the last 60 minutes to more coherently visualize the results. 

Again, the Optimus Eco gives Intel's SSD DC S3700 a run for its money. The Intel drive's consistency is slightly better, but SanDisk still does well. Every single one-second average falls between 28,500 and 38,000 IOPS (0.84 and 1.12 ms), while 73% are above 33,000 IOPS.

Looking at a histogram of the data, we see a nice, even distribution. Often when we generate this data, we see a high concentration centered around the vendor's claimed spec, but a non-trivial amount of data landing at higher latency levels. Typically, we attribute that to wear leveling or garbage collection. Even Intel's SSD DC S3700 exhibits some of that behavior.

The Eco isn't like that. Although the S3700 demonstrates better performance consistency, it is only slightly better, and that advantage probably won't be noticeable in real-world apps.

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