The first step is installing the database that sits at the heart of the cluster. When we talk about High Availability, we talk about several databases (for redundancy) and a means to keep them synchronized. In this case, we must choose the MySQL database, along with Galera for synchronous multi-master replication. The choice of database isn’t a foregone conclusion; you’re not required to use MySQL. It is, however, a fairly common choice in OpenStack installations, so we’ll cover it here.