Apologies for the delayed reply. As long as the MySQL/MariaDB servers are configured correctly then the replication is fully automatic and should one of them be offline for any period, it will synchronise with the other server once it is back. This allows us to take one of the servers down for upgrades, etc. without any effect on the service.

I’m sure I have some notes on the configuration somewhere…

I haven’t used MariaDB yet but will be in the next couple of weeks for a large database (using Piwik).

We’re moving from MySQL 5.1 to MariaDB 5.5 as the later versions (5.4+, I seem to recall) have multi-threaded support. Otherwise only a single CPU core can be used which seriously affects performance.