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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 which 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.

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 MX300's peak speeds are right up there with the MX200's. This drive's steady-state speeds just can't compete with its predecessor's, though. Dynamic Write Acceleration makes the drive go like hell when it can, but once those tricks are exhausted, even 3D TLC can't stand up to good old MLC NAND.

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.

It's a pretty gentle slope, but it does go up. We like it when SATA drives scale even a little bit. Let's see how the MX300's scaling compares to the rest of the Crucial lineup.

No touching! Amusingly, the scaling curves of the Crucial drives don't end up intersecting at all. If queue depth scaling with a database access pattern is important to you, Crucial offers four distinct, non-overlapping behaviors to pick from. Choose your own adventure.

On the next page we put aside IOMeter to see how the MX300 performs with real-world file I/O.