4 ms·

Thanks, very informative! One more thing, I'm surprised that 4KB blocks are relevant, I'd have thought that disk requests in benchmarking (edit: cos manufactur

Thanks, very informative! One more thing, I'm surprised that 4KB blocks are relevant, I'd have thought that disk requests in benchmarking (edit: cos manufacturers like to cheat), and a lot of reads in the real world, would operate at much larger requests than 4K. Is it that IOs are broken down to 4K blocks at the disc controller level, or is that done deliberately in benchmarking to stress the IO subsystem?

wtallis 7y ago
SSDs are traditionally marketed with sequential IO performance expressed in MB/s or GB/s, and random IO performance expressed in 4kB IOs per second (IOPS). Using larger block sizes for random IO will increase throughput in terms of GB/s but will almost always yield a lower IOPS number. Block sizes smaller than 4kB usually don't give any improvement to IOPS because the SSD's Flash Translation Layer is usually built around managing data with 4kB granularity.
- tempguy9999 7y ago
  > expressed in 4kB IOs per second (IOPS). Using larger block sizes for random IO will increase throughput in terms of GB/s but will almost always yield a lower IOPS number and higher IOPs numbers give the marketing department the warm and fuzzies. Got it.
  - mlyle 7y ago
    It is a good metric because it is a measure of random access. Bigger requests are a mixed measure of sequential performance and random access (and you can basically infer the performance for any io size from the huge request bandwidth and the smallest reasonable IO IOPS)