From: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
---|---|
To: | Lonni J Friedman <netllama(at)gmail(dot)com> |
Cc: | Craig Ringer <ringerc(at)ringerc(dot)id(dot)au>, Jerry Sievers <gsievers19(at)comcast(dot)net>, Magnus Hagander <magnus(at)hagander(dot)net>, pgsql-admin(at)postgresql(dot)org |
Subject: | Re: pg_basebackup blocking all queries with horrible performance |
Date: | 2012-06-09 06:53:35 |
Message-ID: | CAOR=d=1vLOBPXcBhM+7kkUMFAb4oJpJREOxYqepHZX9o+ZyDuQ@mail.gmail.com |
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Lists: | pgsql-admin pgsql-hackers |
On Fri, Jun 8, 2012 at 1:30 PM, Lonni J Friedman <netllama(at)gmail(dot)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.
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