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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 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.


Samsung's V-NAND drives may hit higher peak speeds, but they don't hold on to them for quite as long as the XG5 does. The drive's steady-state speeds seem close to on par with the 960 EVO 1TB. Let's look at the actual numbers to confirm.

The 960 EVO 1TB wins here, but the gains Toshiba's made over the OCZ RD400 are astounding. The XG5's peak and steady-state write rates are almost double those of the RD400.

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 XG5 scales well until QD32, after which it levels off. This performance is another big win over the RD400, which only makes it to QD8 before fizzling out. Let's take a look at a few of the contenders side-by-side.


The XG5 and RD400 are neck-and-neck until QD4, at which point the XG5 starts to drastically outpace its planar cousin. The 960 EVO 1TB scales a little faster and further than the XG5, but the Toshiba drive remains within striking distance.

Our scaling and sustained IOMeter tests gave Toshiba's BiCS drive a big lead over the older, planar 15-nm MLC one. Samsung's 1TB V-NAND drive maintains an edge, but the XG5 may yet give it reason to start sweating. Let's move on to real-world performance tests.