How can i view the disk latency of a ZFS pool, or of the disks in it?

Question

I'm using FreeBSD. I would like to write a munin plugin to log it, but i don't understand how to get this data.

Answer 1

I don't believe there's a way to measure this directly without abusing dtrace.

Some things that may be helpful:

• gstat(8) - Geom device statistics, can show you raw disk activity / workload
  Doesn't directly measure latency though.

• ioping - Lets you measure latency from userland (you could run it & log/chart the results)
  Downside: Adds load to do the test, passes through the VFS layer, and can't test the underlying drive unless you reserve a partition for it to use.