Re: [GENERAL] Slow PITR restore

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On Thu, 13 Dec 2007 11:12:26 -0800
"Joshua D. Drake" <jd(at)commandprompt(dot)com> wrote:

> > > Hmm --- I was testing a straight crash-recovery scenario, not
> > > restoring from archive. Are you sure your restore_command script
> > > isn't responsible for a lot of the delay?
> >
> > Now that's an interesting thought, I will review in the morning when
> > I have some more IQ points back.
>
> As promised :)... I took a look at this today and I think I found a
> couple of things. It appears that once the logs are archived, the
> recovery command copies the archive file to a recovery location and
> then restores the file.
>
> If that is correct that could explain some of the latency I am seeing
> here. Even with the speed of these devices, it is still a 16 MB file.
> That could take 1-2 seconds to copy.
>
> There is also the execution of pg_standby each time as the recovery
> command which although I haven't timed is going to add overhead.
>
> Based on the logs I pasted we are showing a delay of 6, 14, 3, 13, 4
> and then another 6 seconds.
>
> When are fsyncs called on the recovery process?
>
> At these types of delays even speeding the process 2 seconds per log
> is going to be significant.
>
> Sincerely,
>
> Joshua D. Drake
>

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