Sustained and scaling I/O rates
Our sustained IOMeter test hammers drives with 4KB random writes for 30 minutes straight. It uses a queue depth of 32, a setting that should result in higher speeds that saturate each drive's overprovisioned area more quickly. This lengthy—and heavy—workload isn't indicative of typical PC use, but it provides a sense of how the drives react when they're pushed to the brink.
We're reporting IOps rather than response times for these tests. Click the buttons below the graph to switch between SSDs.
Hm. Something odd is going on here. For the first several minutes of the test, the 960 Pro gasps and wheezes at barely over 100 IOps. Then it springs to life, jumping to heights only probed by Intel's NVMe drives before now. We re-ran our sustained tests a few extra times without getting meaningfully different results. We saw this sort of behavior before back when we reviewed the Intel 750 Series drives, but we never reached a satisfactory conclusion as to why it occurred. We've reached out to Samsung in case the company can shed any light on the situation.
To show the data in a slightly different light, we've graphed the peak random-write rate and the average, steady-state speed over the last minute of the test.
Luckily for the 960 Pro, these graphs don't capture the sluggish start—they only care about peak speed and the steady-state speed reached near the end of the time period. Both of those metrics cast the 960 Pro in a wonderful light.
Our final IOMeter test examines performance scaling across a broad range of queue depths. We ramp all the way up to a queue depth of 128. Don't expect AHCI-based drives to scale past 32, though—that's the maximum depth of their native command queues.
For this test, we use a database access pattern comprising 66% reads and 33% writes, all of which are random. The test runs after 30 minutes of continuous random writes that put the drives in a simulated used state. Click the buttons below the graph to switch between the different drives. And note that the P3700 plot uses a much larger scale.
Another record for the 960 Pro! It's the first drive since the P3700 to force us to alter the standard 0-to-35000 IOps scale we like to use for this graph. The 960 Pro scales far better than anything we've seen recently. It offers nearly linear scaling until QD32. The 950 Pro didn't scale anything like this, as the next set of graphs will make clear.
The 950 Pro of yesteryear scaled up to QD4 but then flatlined. The 960 Pro, on the other hand, outscales even Intel's formidable 750 Series SSD all the way up to QD64, which is where the Samsung drive regresses in speed.
IOMeter synthetics were a massive win for the 960 Pro. Next, we see what kind of performance $1300 gets you in the real world.