Results: Performance Consistency
In the following tests, we subjected our enterprise SSDs to 25 hours of continuous random 4 KB writes across each drive. We recorded the IOPS every second, giving us 90,000 data points. We then zoomed in to the last 60 minutes to more coherently visualize the results.
As you can see from the graph above, the P420m, while delivering high overall average IOPS, also produces some noisy results. Depending on your take, the P420m actually performs better than the P320h at a queue depth of 32. In terms of consistency, though, the P320h is still a far superior drive. At a queue depth of 256, the P320h takes a clear and commanding lead.
The consistency graph doesn't always tell the whole story because outliers show up more prominently than clusters of points. When looking at the histogram, you can see that roughly 70% of the data-points meet Micron's specification. Compare that to the P320h at a queue depth of 256, where 87% of the data points are at or above the specification, and 99% fall within 97.5% of its spec. Looking at the results differently, the P420m has a standard deviation of 16,000 IOPS, while the P320h's is only 4,000 IOPS.
