On Fri, Jun 8, 2012 at 1:30 PM, Lonni J Friedman <netllama@gmail.com> wrote:
> I've looked at iostat output both before & during pg_basebackup runs,
> and I'm not seeing any indication that the problem is due to disk IO
> bottlenecks. The numbers don't vary very much at all between the good
> & bad times. This is typical when pg_basebackup is running:
> ########
> Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s
> avgrq-sz avgqu-sz await r_await w_await svctm %util
> md0
> 0.00 0.00 67.76 68.62 4.42 1.46
> 88.34 0.00 0.00 0.00 0.00 0.00 0.00
> ########
>
> and this is when the system is ok:
> ########
> Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s
> avgrq-sz avgqu-sz await r_await w_await svctm %util
> md0
> 0.00 0.00 68.04 68.56 4.44 1.46
> 88.39 0.00 0.00 0.00 0.00 0.00 0.00
> ########
Two points. 1: md0 don't show things like %util, only the physical
drives will have that output, which is what you want to see, if it's
hopping up to 100%. 2: you need to run it with a number and get
something AFTER the first line, which is the average since the machine
was first turned on.