Re: Streaming replication document

On 04.12.2010 04:18, Tatsuo Ishii wrote:
> There is a description about streaming replication in the doc:
> ----------------------------------------------------------
> 25.2.5. Streaming Replication
>
> :
> :
> If you set up a WAL archive that's accessible from the
> standby, wal_keep_segments is not required as the standby can always
> use the archive to catch up.
> ----------------------------------------------------------
>
> I think this description is somewhat inadequate. Since recovery using
> WAL archive is file based, it may cause long replication delay. I
> think even if WAL archive is set up, we should set wal_keep_segments
> to proper value, not 0. Recovery from WAL archive should be the last
> resort, shouldn't be?

If your standby falls behind that much, catching up is going to take a 
while anyway. The master always keeps 2-3 * checkpoint_segments WAL 
segments around anyway even if wal_keep_segments is 0.

Depending on the archive, it might well be faster to catch up using the 
archive, instead of streaming from master.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com