Resilence: Multi-master setups with MySQL/MariaDB
For mission critical sites, having dual masters can be the difference between staying online, and encountering major problems.
Hardware will fail and other issues will occur - the trick is to make sure that such failures don't cause emergencies.
In addition, dual master setups enable maintenance including server upgrades without scheduled downtime.
Open Query deploys dual master setups for most of its clients, using the MMM tool. There's no secret juice and we're happy to share what we know.