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> NVMe is actually not any better than SATA SSDs at random/low-queue-depth IO. The fastest NVMe SSD[0] on UserBenchmark appears to be a fair bit faster at 4k r

> NVMe is actually not any better than SATA SSDs at random/low-queue-depth IO. The fastest NVMe SSD[0] on UserBenchmark appears to be a fair bit faster at 4k random read compared to the fastest SATA SSD[1]. 75 MB/s vs 41.9 MB/s Avg Random 4k Read. 1,419 MB/s vs 431 MB/s Avg Deep queue 4k read Edit: This comment has been edited, originally I was comparing a flash SATA SSD vs an optane nvme drive, which wasn't a fair comparison. [0]: https://ssd.userbenchmark.com/SpeedTest/1311638/Samsung-SSD-980-PRO-250GB https://ssd.userbenchmark.com/SpeedTest/1311638/Samsung-SSD-... [1]: https://ssd.userbenchmark.com/SpeedTest/1463967/Samsung-SSD-870-EVO-2TB https://ssd.userbenchmark.com/SpeedTest/1463967/Samsung-SSD-...

paulmd 4y ago
that might be with a higher queue depth though, like 4K Random QD=4 or something, I don't see it says "QD=1" or similar anywhere there and that's a fairly high result if it was really QD=1. It's true that NVMe does better with a higher queue depth though, but, consumer workloads tend to be QD=1 (you don't start the next access until this one has been finished) and that's the pathological case due to the inherent latency of flash access. Flash is pretty bad at those scenarios whether SATA or NVMe. https://images.anandtech.com/graphs/graph11953/burst-rr.png https://images.anandtech.com/graphs/graph11953/burst-rr.png https://www.anandtech.com/show/11953/the-intel-optane-ssd-900p-review/7 https://www.anandtech.com/show/11953/the-intel-optane-ssd-90... So eh, I suppose it's true that NVMe is at least a little better in random 4K QD=1, a 960 Pro is 59.8 MB/s vs 38.8 for the 850 Pro (although note that's only a 256GB drive, which often don't have all their flash lanes populated and a 1TB or 2TB might be faster). But it's not really night-and-day better, they're still both quite slow. In contrast Optane can push 420-510 MB/s in pure 4K Random QD=1.

paulmd 4y ago

that might be with a higher queue depth though, like 4K Random QD=4 or something, I don't see it says "QD=1" or similar anywhere there and that's a fairly high result if it was really QD=1. It's true that NVMe does better with a higher queue depth though, but, consumer workloads tend to be QD=1 (you don't start the next access until this one has been finished) and that's the pathological case due to the inherent latency of flash access. Flash is pretty bad at those scenarios whether SATA or NVMe. https://images.anandtech.com/graphs/graph11953/burst-rr.png https://images.anandtech.com/graphs/graph11953/burst-rr.png https://www.anandtech.com/show/11953/the-intel-optane-ssd-900p-review/7 https://www.anandtech.com/show/11953/the-intel-optane-ssd-90... So eh, I suppose it's true that NVMe is at least a little better in random 4K QD=1, a 960 Pro is 59.8 MB/s vs 38.8 for the 850 Pro (although note that's only a 256GB drive, which often don't have all their flash lanes populated and a 1TB or 2TB might be faster). But it's not really night-and-day better, they're still both quite slow. In contrast Optane can push 420-510 MB/s in pure 4K Random QD=1.