OpenStack can be backed by a number of database backends, and one of the most common options is MySQL. There are a number of ways to make MySQL more resilient and available. The following approach uses a load balancer to front a multi-read/write master with Galera, taking care of the synchronous replication required in such a setup. The advantage of this is that we are adding resilience in the event of a database node failure, as each node is getting ready.
We'll be using a free online configuration tool from SeveralNines.com to configure a 3-node, multi-master MySQL setup with Galera, monitored using the free cluster management interface, cmon
, using a fourth node. This implies we have four servers available, running Ubuntu (other platforms are supported) with enough memory and disk space for our environment and at least two CPUs available.