Re: PITR Base Backup on an idle 8.1 server

From: Marco Colombo <pgsql(at)esiway(dot)net>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: PITR Base Backup on an idle 8.1 server
Date: 2007-06-06 13:19:16
Message-ID: 4666B454.6030904@esiway.net
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Simon Riggs wrote:
> On Tue, 2007-06-05 at 18:39 +0200, Marco Colombo wrote:
>> I'm asking: what _exactly_ can go wrong?
>
> If a checkpoint occurs while taking the backup then the contents of the
> files will be overwritten
^^^^^
Data files or WAL segments? My archive command prevents WAL segments
from being recycled during the backup.

and you will be unable to rollforward from
> before the backup until after the backup. This will give you the FATAL
> error message "WAL ends before end time of backup dump". You won't know
> this until you have attempted recovery using those files, even if the
> scripts give rc=0.

Well, my procedure currently produces two tar achives. One is the 'base
backup' (a copy of the datafiles). One is a copy of wal segments, right
after the backup. Which one do you expect to be corrupted if a
checkpoint happens during the backup?

.TM.

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