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> especially with NVMe, you don't have to read things sequentially NVMe is actually not any better than SATA SSDs at random/low-queue-depth IO. The latency-pe
by paulmd 4y ago
> especially with NVMe, you don't have to read things sequentially
NVMe is actually not any better than SATA SSDs at random/low-queue-depth IO. The latency-per-request is about the same for the flash memory itself and that's really the dominant factor in purely random requests.
Of course pretty soon NVMe will be used for DirectStorage so it'll be preferable to have it in terms of CPU load/game smoothness, but just in terms of raw random access, SSDs really haven't improved in over a decade at this point. Which is what was so attractive about Optane/3D X-point... it was the first improvement in disk latency in a really long time, and that makes a huge difference in tons of workloads, especially consumer workloads. The 280/480GB Optane SSDs were great.
But yeah you're right that paging and compression and other tricks have let us get more out of the same amount of RAM. Browsers just need to keep one window and a couple tabs open, and they'll page out if they see you launch a game, etc, so as long as one single application doesn't need more than 16GB it's fine.
Also, games are really the most intensive single thing that anyone will do. Browsers are a bunch of granular tabs that can be paged out a piece at a time, where you can't really do that with a game. And games are limited by what's being done with consoles... consoles have stayed around the 16GB mark for total system RAM for a long time now too. So the "single largest task" hasn't increased much, and we're much better at doing paging for the granular stuff.
- vlovich123 4y agoLatency may be similar but: 1. Pretty sure IO depth is as high as OSes can make it so small depth only happens on a mostly idle system. 2. Throughput of NVMe is 10x higher than SATA. So in terms of “time to read the whole file” or “time to complete all I/O requests”, it is also meaningfully better from that perspective.
- WatchDog 4y ago> 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 agothat 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.