David:

Just to un-help you a little bit: one difilculty you can have with
replication used to keep a 24/7 system: you must make shure that every user
fails to connect to the main server before using the backup server. That's
why I change IP adresses in my backup server to match the main.

It could be some cases (it depends on the network layout, where you keep the
servers, the kind of fault, etc) that some users could not access the
primary but still can access the backup server. One more thing to worry
about. In that case you must to replication both ways.

Oh well. That's why clusters are sooooooo expensive.

Artur