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In FreeBSD you can run "top -m io" and it will show you disk io.

For example:

enter image description here

What units is the WRITE/READ in, bytes or kilobytes or megabytes?

  • if I had to guess, it's probably lowest one possible (aka bytes) – alexus Dec 27 '18 at 20:41
  • @alexus well that would be logical however I'm seeing values like 1 and 15 and I doubt that is correct since it doesn't line up with using iostat, it might even represent some other unit completely other than byte. – Exocomp Dec 27 '18 at 21:51
  • Did you look at man top? Also, FreeBSD is not Linux. Removed tag. – Rob Dec 28 '18 at 13:22
  • @Rob dropping some knowledge, ty, I did look at the man page but it was not obvious unless you are indirectly telling me I missed something – Exocomp Dec 28 '18 at 13:24
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The top manual page refers to the getrusage(2) system call which generates the following block device statistics:

ru_inblock the number of times the file system had to perform input.

ru_oublock the number of times the file system had to perform output.

and those numbers have no unit, they seem to be event counters.

  • The unit is right in the name: block – Michael Hampton Dec 28 '18 at 15:01
  • Based on other context in the man page, I'm thinking that block refers to "block device" rather than "blocks of data". So the unit of the counter is most likely "event". Although, a block device isn't a filesystem, so I'm not inclined to trust the authors of that documentation particularly far. – womble Dec 29 '18 at 0:19

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