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IOMeter — Sequential and random performance
IOMeter fuels much of our latest storage test suite, including our sequential and random I/O tests. These tests are run across the full capacity of the drive at two queue depths. The QD1 tests simulate a single thread, while the QD4 results emulate a more demanding desktop workload. For perspective, 87% of the requests in our old DriveBench 2.0 trace of real-world desktop activity have a queue depth of four or less. Clicking the buttons below the graphs switches between results charted at the different queue depths.

Our sequential tests use a relatively large 128KB block size.



Both drives come out of the gate with solid sequential read numbers. They even beat some bigger, fancier drives at a queue depth of one, and the BX200 hangs with the pack at QD4.

But when it comes to sequential write performance? Oh, dear. These are the slowest-writing drives we've seen in a very long time. The BX200 falls especially far behind, losing to even the Intel X25-M G2, a SATA 3Gbps drive that was released in 2009. Yikes. Both drives fall far short of the high bar set by Samsung's TLC in the 850 EVO series—even the 250GB EVO. To be fair, the 850 EVOs are packing 3D V-NAND, not planar NAND. The older, MLC-based Arc 100 and BX100 look very good by comparison.

Next, we'll turn our attention to performance with 4KB random I/O. The tests below are based on the median of three consecutive three-minute runs. SSDs typically deliver consistent sequential and random read performance over that period, but random write speeds worsen as the drive's overprovisioned area is consumed by incoming writes. We've reported average response times rather than raw throughput, which we think makes sense in the context of system responsiveness.



The sequential results are reversed here. The two drives post relatively poor random read response times, but very respectable random write results. On the read side, the BX200 gets beaten again by the six-year-old X25-M G2. When we switch to writes, though, the BX200 manages to beat the BX100. Not too shabby, since we'd expect the BX100's MLC to give it a clear advantage over the BX200. The difference is likely due to the new SLC-esque caching ability that the BX100's controller lacks.

As we noted, the preceding tests are based on the median of three consecutive three-minute runs. SSDs typically deliver consistent sequential and random-read performance over that period, but random-write speeds worsen as the drive's overprovisioned area is consumed by incoming writes. We explore that decline in the next set of tests.