WD Black SN850X with Heatsink 2TB SSD Review

We used CrystalDiskMark 8‘s custom settings to test the 4K random read performance of the drive through a range of queue depths. The setup for the tests is listed below.

Transfer Request Size: 4KB, Outstanding I/O: 1-32.

The official maximum 4K random read figure for the drive is 1.2M IOPS. Using our four threaded tests, the best we saw from the tested drive was 446,377 IOPS nowhere close to the official rating. We did a quick test of the drive using eight threads and got a best test result of 648,467.6 IOPS, still miles away from the official figure.

4K Random Read v QD Performance.

At QDs 1, 2 & 4 the drive hovers around the top five of the drives we've tested to date. However at QD32, the 446,377 IOPS figure from the drive sees it in second place in the chart behind another WD Black drive, the SN770.

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