"...but it could also double as a backup." Take care when treating a high-availability set up such as this as a back up: if you are replicating all the changes

"...but it could also double as a backup." Take care when treating a high-availability set up such as this as a back up: if you are replicating all the changes between 2 database servers and an application error (e.g. not a database outage) causes some kind of data corruption, you are hosed if the corruption replicates and you don't also have some previous "snapshot" of the data that you can roll back to.