With PAM 3.3.x or 3.4.x - we introduced the concept of a quorum in our clustering technology.
Historically in old versions of PAM 3.2.x and below, when any member of the primary site went out of sync - you would have to stop the cluster and restart it - causing a temporary outage.
So if you currently have 2 members of your cluster in a good standing, you can always add a 3rd member in without bringing the cluster in.
On the 3rd member you would into the:
PAM UI >> Configuration >> Clustering
- The first step would be making sure the Key is the same from the other members.
- Than on the Global Settings -> select "Load Configuration from member" -> than enter the ip address for your primary master member.
- After it loads -> go into Global Settings -> "Primary Site" -> and add this machine to the list and click save.
- Than on the bottom, click "Save Config Locally"
After doing this, you than can click on "Subscribe to Active Cluster" -> which will add this server into the cluster without stopping it.