Re: Online Backup and WAL archives

You may need to recreate some indexes:

"Operations on non-B-tree indexes (hash, R-tree, and GiST indexes) are not
presently WAL-logged, so replay will not update these index types. The
recommended workaround is to manually REINDEX each such index after
completing a recovery operation."

Best Regards,
Bruno Almeida do Lago

-----Original Message-----
From: pgsql-admin-owner(at)postgresql(dot)org
[mailto:pgsql-admin-owner(at)postgresql(dot)org] On Behalf Of Morus Walter
Sent: Tuesday, February 01, 2005 10:59 AM
To: pgsql-admin(at)postgresql(dot)org
Subject: [ADMIN] Online Backup and WAL archives

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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