Memory is slow, Disk is fast
4 points by typesanitizer
4 points by typesanitizer
Sure, disk is fast when you’ve got “8 Samsung PM983 NVMe drives over NVMe-oF on four 100 Gb InfiniBand links.” But that’s not cause to make blanket assertions about performance. Outside of high-end servers, I don’t think many programs have access to that much I/O bandwidth.
A low end SSD is still hundreds of megs per second. It's not blazingly fast, but many programs still can't saturate it on a desktop class CPU.
I'd be surprised if you can even buy new SSDs that slow nowadays. The SN770 NVMe drives in my home desktop computer top out at 4.5 GB/s for reads on the SEQ1MQ8T1 benchmark and that's not the state of the art. I realize speccing servers for scale-out is highly cost sensitive but that's a massive gulf. If you need a ridiculous amount of cost-effective storage wouldn't you opt for a large pool of HDDs and a small pool of actually fast SSDs as cache or local storage? Not a rhetorical question--I'm legitimately curious.