We did some tests with Drupal 5 & master-master replication and it's not that simple. The master-master setup itself is no problem, but master-master breaks the sequences concept (db_next_id()) in Drupal and it also causes problems in the caching tables. We quickly gave up with it. We still use master-master for high availability, but point all our frontend servers to the same DB-server. You still need to be able to handle all load with one server that way, but it makes it easier to failover.
Master-master should become easier with Drupal 6, I'll try to do some tests with it once I have time.
We did some tests with Drupal 5 & master-master replication and it's not that simple. The master-master setup itself is no problem, but master-master breaks the sequences concept (db_next_id()) in Drupal and it also causes problems in the caching tables. We quickly gave up with it. We still use master-master for high availability, but point all our frontend servers to the same DB-server. You still need to be able to handle all load with one server that way, but it makes it easier to failover.
August 24, 2007 - 20:07Master-master should become easier with Drupal 6, I'll try to do some tests with it once I have time.