3 ms·
Thank you for engaging. Also, thank you for finding that imprecise language. An original draft had stated that I'm talking about I/O duration, but I lost that
by dmazin 3y ago
Thank you for engaging.
Also, thank you for finding that imprecise language. An original draft had stated that I'm talking about I/O duration, but I lost that language. I will re-add it.
My numbers are for "main memory access", "SSD I/O" and "rotational disk I/O" from Gregg System Performance (chapter 2). In retrospect, with all respect to Gregg, that wording is itself pretty imprecise.
I think what really matters here is I/O duration rather than throughput. That is, the reason we use the cache so much is because a single I/O is really slow against disks...
- jchw 3y agoYeah, that's true. Raw speeds don't really mean a whole lot without more context, and in practice writing to disk is going to be a lot slower even if the peak throughputs are not quite that far off. The performance characteristics are quite different in practice. I assume at one point in history though, these numbers were closer to true even for raw throughput... PCIe and NVMe have probably helped close the gap a bit, I would guess.