Measure disk I/O in Ubuntu


Q. I think I'm having disk I/O problems on my system. How do I check what it is or measure it?

A. First, you'll have to install some applications/tools:

apt-get install sysstat
apt-get install iotop

iotop command, much like top, will give you the real-time overview of your Read/Write requests. It's fun to look at, but we find useless for measuring I/O.

If you want some data that gives you an average, you should probably run something like this:

iostat -dkx

Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util
sda 0.04 321.99 1.12 16.63 68.11 1354.49 160.26 5.04 284.09 4.05 7.19


If the %util is too high (above 75-80%), you have a bottleneck.