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 SU800's sustained random performance echoes the results we saw in our sequential write tests. We expect to see drives hit a high peak early on in this test, then eventually settle down to a much lower steady-state speed as their caching schemes and overprovisioning are overwhelmed. In the SU800's case, its cache has given up the ghost already by the time the test begins. All we have here is 30 minutes of relatively slow writes.
But that's not to say that the actual steady-state speed is necessarily bad. 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.
The SU800's steady-state TLC write rate is actually quite good, narrowly beating the 850 EVO's TLC V-NAND and even the planar MLC in the MX200. And it's almost double that of the MX300. Not bad at all, in context.
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 SU800's humdrum scaling won't get anybody's heart pounding, but it's no more humdrum than any run-of-the-mill SATA drive. In fact, you may notice that the scaling curves are quite similar to Adata's SP550. Let's plot 'em against each other to try and spot the differences.
The JMicron controller in the XPG SX930 afforded it little scaling performance. The Marvell chip in the MX300 scaled almost linearly as queue depth increased. The Silicon Motion-equipped SP550 and SU800 have a bit more ebb and flow to their curves than the MX300 did, but the end results don't look all that different from the MX300's.
The SU800 can now breathe a sigh of relief, since we're putting IOMeter aside to explore some real-world testing with RoboBench.
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