On 29.09.2010 11:46, Fujii Masao wrote:
> Aside from standby registration itself, I have another thought for C). Keeping
> many WAL files in pg_xlog of the master is not good design in the first place.
> I cannot believe that pg_xlog in most systems has enough capacity to store many
> WAL files for the standby.
>
> Usually the place where many WAL files can be stored is the archive. So I've
> been thinking to make walsender send the archived WAL file to the standby.
> That is, when the WAL file required for the standby is not found in pg_xlog,
> walsender restores it from the archive by executing restore_command that users
> specified. Then walsender read the WAL file and send it.
>
> Currently, if pg_xlog is not enough large in your system, you have to struggle
> with the setup of warm-standby environment on streaming replication, to prevent
> the WAL files still required for the standby from being deleted before shipping.
> Many people would be disappointed about that fact.
>
> The archived-log-shipping approach cuts out the need of setup of warm-standby
> and wal_keep_segments. So that would make streaming replication easier to use.
> Thought?
The standby can already use restore_command to fetch WAL files from the
archive. I don't see why the master should be involved in that.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com