Poor Disk Performance 09 May 2021 People often tell me they don't understand performance tool output because they can't tell what's "good" or "bad." It can be hard as performance is subjective. What's good for one user may be bad for another. There are also cases where I can't tell either: The tools only provide clues for further analysis. I recently encountered terrible disk performance and thought it'd be useful to collect Linux tool screenshots and share them for reference. E.g., iostat(1): $ iostat -xz 10 [...] Device r/s w/s rkB/s wkB/s rrqm/s wrqm/s %rrqm %wrqm r_await w_await aqu-sz rareq-sz wareq-sz svctm %util