Re: How to get disk I/O wait time

On Sat, Oct 15, 2016 at 7:23 AM, <[email protected]> wrote:

> I had a question about disk I/O wait time. Is it a way to get these stats
> with pcp?
>
> William Staten
>

Hi William, yes disk I/O wait time is available and can be reported with
the pcp-iostat(1) command line tool, e.g.

# pcp iostat -t 5
# Device     rrqm/s wrqm/s   r/s  w/s  rkB/s  wkB/s avgrq-sz avgqu-sz await
r_await w_await %util
sda               1      3     1    4      7     83     18.8      0.0     2
      1       2     1
...

The default units in the above report are 'average milliseconds per
request'.

There are also 'derived' metrics defined in
/var/lib/pcp/config/derived/iostat.conf for wait time and related metrics,
see the definitions in that file. These metrics can be reported on the
command line with generic tools such as pmrep and pmval and others. There
is also a pmchart configuration for displaying iostat metrics graphically,
e.g. pmchart -c Iostat

Finally, in addition to disk.dev.* metrics (scsi devices), we also have
disk.dm.* (device mapper devices such as LVM and multipath, etc) and
disk.md.* (for multiple devices). To list all the related metrics and their
respective metadata: pminfo -m -d disk.{dev,md,dm}

Regards
-- Mark