Results: Performance Consistency
We also pay a lot of 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 appears equal. Viewing the data with more granularity gives us insight on particular drive behaviors.
For the following tests, Samsung's 845DC EVO and three comparison SSDs are subjected to 25 hours of continuous random 4 KB writes. 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.
The 845DC EVO demonstrates good consistency in our latency tests, surpassing Intel's SSD DC S3500 and Samsung's own SM843. It isn't able to keep pace with Micron's M500DC, which is still a steal considering $/IOPS.
Samsung can be proud that more than 98% of all 1 s averages are better than the 14,000 IOPS specification. In fact, the lowest 1 s average is over 13,000 IOPS, which is still good for this market segment.
The histogram shows us a clean distribution without any major outliers. In this view, we see that the data points form an almost perfect bell curve, with the overall average latency contained within the largest bin of the histogram.
Looking at the first nine hours of write testing shows us that the 240 and 960 GB models perform similarly. You can see the effect of having more available NAND for over-provisioning, though. The 240 GB model exits its fresh-out-of-box condition and enters steady-state much more quickly than the 960 GB model. In fact, that latter implementation doesn't hit steady state until 12 hours after we begin the tests.
I also observed that, during the first 50 minutes, while still in the fresh out of box state, Samsung's 845DC EVO hit an incredibly stable 80,000 IOPS.