The official 4K random read figure for the 1TB SN850 is up to 1,000,000 IOPS. With our test platform and four-threaded testing, the drive got nowhere near that official maximum figure, the best we saw was 430,473 IOPS. We did a quick test using 16 threads at a queue depth of 32 and saw the performance rise to 742,492 IOPS, still well short of the official maximum.
4K Random Read v QD Performance Comparison
At a QD of 1, the WD Black SN850 trails the Samsung SSD980 PRO but after that, the WD drive rules the roost of all the tested queue depths.