Online Backup and WAL archives - Mailing list pgsql-admin

From Morus Walter
Subject Online Backup and WAL archives
Date
Msg-id 16895.32035.914311.612690@tanto-xipolis.de
Whole thread Raw
Responses Re: Online Backup and WAL archives  ("Bruno Almeida do Lago" <teolupus@gmail.com>)
Re: Online Backup and WAL archives  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Online Backup and WAL archives  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-admin
Hi,

I'm currently considering to use postgresql 8.0 online backups.

The documentation says
' To make use of this backup, you will need to keep around all the
WAL segment files generated at or after the starting time of the backup. '

Now I'm wondering how much of these WAL segment files do I really need
in order to recover the databases to a consistent state.

Let's say I cannot write the WAL segments to tape dynamically when they
are archived. Then a complete disk failure would mean, that I loose WAL
segments also.
Therefore I would like to save a minimum number of WAL segments at or
after the online backup that allows recovery.
Is that possible? How would I decide how much of the WAL I need?

Of course I could recover to the state of database at about the time of the
backup only, but it would be a consistent state at least.

Or should I use the previous online backup plus all WAL segements up to
the current backup?

I expect the online backup to faster on recovery than an SQL dump, since
the latter would imply recreation of indexes during recovery.
Therefore I would prefer to use online backups.

Morus


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