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by al2o3cr 3080 days ago

    hard disk xfer is 500 MB/s
You need better disks. The one in the laptop I'm typing this on can do 2GB/s, which greatly weakens your comparison.
2 comments

They won't be able to achieve anything like 2GB/s when handling reads from swap, because they are likely to be lots of small chunks of reads - the pages being swapped in are often 4k and will be very difficult to predict, so bulk I/O will be unlikely. Same goes for writes, with the added proviso that your SSDs will have far worse small file write performance than reads, which is probably the 2GB/s headline figure.

A better statistic to use is how many IOPS the disk can handle.

If I may ask, which disks are you using?
the highest end NVMe SSDs can sustain those multi-gigabyte/second reads. https://smile.amazon.com/Samsung-950-PRO-Internal-MZ-V5P512B... for instance.

not sure even they could pull off those speeds with random reads, though.

I think when most people say "hard disk", they usually mean rotating discs that use magnetism to store data. That is what I took tmyklebu's question to mean, since I too have never heard of a HDD reaching anywhere near 2 GB/s.
> I think when most people say "hard disk", they usually mean rotating discs that use magnetism to store data.

while i would personally avoid referring to an SSD as a "hard disk", i was attempting to interpret the original claim in the most charitable possible fashion, since it was utterly absurd if interpreted strictly.

Either way, I learned something. I can picture an array of 20 disks sustaining 2GB/s, but you aren't going to fit 20 disks into a laptop. I didn't realise a high-end SSD could get there, or even how much better regular SSDs are for throughput. (That cost per TB, though!)