Re: replication in Postgres

On 11/25/07, Glyn Astill <glynastill@yahoo.co.uk> wrote:
> So far the only methods I see would be usable for us are Slony I and
> WAL log shipping.

WAL shipping probably does not work the way you think it does. The
secondary server that receives the log pieces is not actually able to
serve any queries; it only processes them as part of a sort of
indefinitely extended recovery procedure. Therefore, the current
shipping support is only good for maintaining a "warm standby" server.
The manual explains this in detail.

Someone is working on extending the current system to allow read-only
queries on a standby server [1], thus making it a "hot standby", but
this feature apparently won't be included until 8.4 [2].

[1] http://archives.postgresql.org/pgsql-hackers/2007-02/msg01390.php
[2] http://archives.postgresql.org/pgsql-general/2007-09/msg00752.php

Alexander.