Comment Re:Clustering (Score 1) 330
Slony-I is intended to be an add-on to postgres and not part of the core. The reason for this is that slony upgrades are supposed to be separate from database upgrades. This allows you to use switchover to minimise the downtime of an upgrade. To upgrade from postgres 8.0 to 8.1 (currently running slony 1.1.2 on all databases, I think), we will be doing the following:
Upgrade to slony 1.1.5 at all nodes simultaneously (should require no more than 5 minutes of slony outage). This does not affect the production database at all.
Wait for slony to catch back up.
Pause replication, again not affecting production.
Upgrade subscriber database to 8.1 (full dump and restore required, or just drop the subscriber db, attach a new 8.1 subscriber db and do a sync).
Unpause replication.
Wait for slony to catch-up.
Switchover from the 8.0 database to the 8.1 database (just a few minutes of downtime).
Pause slony.
Upgrade the original provider database to 8.1.
The versions of slony at both the provider and subscriber must be compatible at all times. Keeping slony versioning separated from the versioning of postgres makes this much easier.
Upgrade to slony 1.1.5 at all nodes simultaneously (should require no more than 5 minutes of slony outage). This does not affect the production database at all.
Wait for slony to catch back up.
Pause replication, again not affecting production.
Upgrade subscriber database to 8.1 (full dump and restore required, or just drop the subscriber db, attach a new 8.1 subscriber db and do a sync).
Unpause replication.
Wait for slony to catch-up.
Switchover from the 8.0 database to the 8.1 database (just a few minutes of downtime).
Pause slony.
Upgrade the original provider database to 8.1.
The versions of slony at both the provider and subscriber must be compatible at all times. Keeping slony versioning separated from the versioning of postgres makes this much easier.
