Having dual masters is useful, not just for redundancy/resilience, but also for regular maintenance purposes. Managing it is a bit more tricky, but the MMM can help.

This talk will show you how to setup a cluster of MySQL servers that use the MMM software to create the ability to have Master-Master Active-Passive failover. An explanation of the software involved and the structure needed, as well as an in-dept overview of what is needed will be given.