Galera Cluster - 3rd Quoroum Only Node - No Replication - Possible?HowTo? I want to setup a 2 node cluster for MariaDB Galera cluster. What I read says it "requires" 3 nodes minimum. This is not correct, I am familiar with HA through using pacemaker, and basically, with only 2 nodes, you don't have quorum, which Galera Cluster Uses.

I found a good article, which basically explains, the 2 options I already figured existed.

Option 1:

Disable Quorum Check

SET GLOBAL wsrep_provider_options='pc.ignore_sb=TRUE';


Option 2:

Post Split-Brain, manually tell a node to become Primary

SET GLOBAL wsrep_provider_options='pc.bootstrap=YES';


What I'd like, is to set up a 3rd VM, that doesn't replicate any DB's, but acts an a quorum box.

Is this possible? Any links on HowTo? - Maybe I am over-thinking this, is there a way to join a cluster, but not define any Databases to replicate? (Seemed to me when I set up Galera that it just replicated everything automatically, which is good, but I'm not so sure there is a "don't replicate option")

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