I have two node active-passive cluster.
If a cluster splits into two (or more) groups of nodes that can no longer communicate with each other (aka. partitions), quorum is used to prevent resources from starting on more nodes than desired, which would risk data corruption. A cluster has quorum when more than half of all known nodes are online in the same partition
By the above definition, a two-node cluster would only have quorum when both nodes are running. This would make the creation of a two-node cluster pointless, but corosync has the ability to treat two-node clusters as if only one node is required for quorum. The pcs cluster setup command will automatically configure two_node: 1 in corosync.conf, so a two-node cluster will "just work".
Here's my config:
So how can the cluster now decide which one has quorum?