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Update recovery documentation.

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Simon Riggs
This commit is contained in:
Bruce Momjian 2006-10-02 22:33:02 +00:00
parent 26ffa627ac
commit 5d52ad9dc8
1 changed files with 51 additions and 1 deletions
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doc/src/sgml/backup.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.88 2006/09/19 19:04:51 neilc Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.89 2006/10/02 22:33:02 momjian Exp $ -->
<chapter id="backup">
<title>Backup and Restore</title>
@ -1167,6 +1167,48 @@ restore_command = 'copy /mnt/server/archivedir/%f "%p"' # Windows
</para>
</sect2>
<sect2 id="backup-incremental-updated">
<title>Incrementally Updated Backups</title>
<indexterm zone="backup">
<primary>incrementally updated backups</primary>
</indexterm>
<indexterm zone="backup">
<primary>change accumulation</primary>
</indexterm>
<para>
Restartable Recovery can also be utilised to offload the expense of
taking periodic base backups from a main server, by instead backing
up a Standby server's files. This concept is also generally known as
incrementally updated backups, log change accumulation or more simply,
change accumulation.
</para>
<para>
If we take a backup of the server files whilst a recovery is in progress,
we will be able to restart the recovery from the last restartpoint.
That backup now has many of the changes from previous WAL archive files,
so this version is now an updated version of the original base backup.
If we need to recover, it will be faster to recover from the
incrementally updated backup than from the base backup.
</para>
<para>
To make use of this capability you will need to set up a Standby database
on a second system, as described in <xref linkend="warm-standby">. By
taking a backup of the Standby server while it is running you will
have produced an incrementally updated backup. Once this configuration
has been implemented you will no longer need to produce regular base
backups of the Primary server: all base backups can be performed on the
Standby server. If you wish to do this, it is not a requirement that you
also implement the failover features of a Warm Standby configuration,
though you may find it desirable to do both.
</para>
</sect2>
<sect2 id="continuous-archiving-caveats">
<title>Caveats</title>
@ -1317,6 +1359,14 @@ restore_command = 'copy /mnt/server/archivedir/%f "%p"' # Windows
really offers a solution for Disaster Recovery, not HA.
</para>
<para>
When running a Standby Server, backups can be performed on the Standby
rather than the Primary, thereby offloading the expense of
taking periodic base backups. (See
<xref linkend="backup-incremental-updated">)
</para>
<para>
Other mechanisms for High Availability replication are available, both
commercially and as open-source software.