Re: Continuous archiving and wal generation

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Mikko Partio" <mpartio(at)gmail(dot)com>,<pgsql-admin(at)postgresql(dot)org>
Subject: Re: Continuous archiving and wal generation
Date: 2007-10-19 14:57:07
Message-ID: 47187F73.EE98.0025.0@wicourts.gov
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>>> On Fri, Oct 19, 2007 at 1:40 AM, in message
<2ca799770710182340y9877687i8e82cd6847f37c5a(at)mail(dot)gmail(dot)com>, "Mikko Partio"
<mpartio(at)gmail(dot)com> wrote:
>
> To make use of the backup, you will need to keep around all the WAL segment
> files generated during and after the file system backup. To aid you in doing
> this, the pg_stop_backup function creates a *backup history file* that is
> immediately stored into the WAL archive area. This file is named after the
> first WAL segment file that you need to have to make use of the backup. For
> example, if the starting WAL file is 0000000100001234000055CD the backup
> history file will be named something like
> 0000000100001234000055CD.007C9330.backup.
>
> My question is: if I have a large database which takes some time to backup
> with tar, and during the interval between pg_start_backup() and
> pg_stop_backup() more than one wal file gets generated, do I have to store
> in addition to the base backup all wal files generated during the backup
> interval or just the one specified by the .backup file?
>
> I'm trying to figure out the minimum required to restore from a backup

If you look inside that backup file, you'll see something like this:

START WAL LOCATION: 47/11B7E980 (file 000000010000004700000011)
STOP WAL LOCATION: 47/13006410 (file 000000010000004700000013)
CHECKPOINT LOCATION: 47/11B7E980
START TIME: 2007-10-12 19:00:02 CDT
LABEL: 2007-10-12_190002
STOP TIME: 2007-10-12 20:10:30 CDT

It tells you what files you need, as a minimum, to restore.

-Kevin

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