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.
The SU900's peak speeds are extremely high, but it can't hold on to them for very long. It oscillates rapidly before quickly collapsing to a low steady-state rate. Let's see what the actual numbers are.
The SU900's peak is the highest we've seen from a 250GB-class drive, whether SATA or PCIe. It's important to bear in mind that the drive can't sustain that rate for any substantial time period. Its steady-state speeds, by contrast, are quite pedestrian. Not markedly worse than other 250GB-class drives, but not better either.
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.
The SU900's scaling curve is barely a curve. The drive doesn't exhibit any willingness to ramp up performance as queue depth increases. At least its speeds didn't regress. Just for fun, let's compare it to some other drives.
The SU800 512GB, SP550 480GB, and MX300 750GB aren't particularly inclined to scale with queue depth, but their results look downright curvaceous next to flatlands of the SU900.
The SU900 didn't hit us with any nasty surprises during our sustained and scaling testing. Everything falls in line with expected performance for a 250GB-class SATA drive. Next up, real-world tests.