Galera Cluster - 3rd Quoroum Only Node - No Replication - Possible?HowTo?
The GALERA ARBITRATOR is exactly what I needed.


The recommended deployment of Galera Cluster is that you use a minimum of three instances. Three nodes, three datacenters and so on.


In the event that the expense of adding resources, such as a third datacenter, is too costly, you can use Galera Arbitrator. Galera Arbitrator is a member of the cluster that participates in voting, but not in the actual replication."



Galera Arbitrator serves two purposes:


When you have an even number of nodes, it functions as an odd node, to avoid split-brain situations.
It can request a consistent application state snapshot, for use in making backups.


HowTo:

http://galeracluster.com/documentation-webpages/arbitrator.html