Cluster networks

Cluster nodes communicate with each other over communication networks.

If one of the physical network interface cards on a node on a network fails, PowerHA® SystemMirror® preserves the communication to the node by transferring the traffic to another physical network interface card on the same node. If a "connection" to the node fails, PowerHA SystemMirror transfers resources to another node to which it has access.

In addition, RSCT sends heartbeats between the nodes over the cluster networks to periodically check on the health of the cluster nodes themselves. If PowerHA SystemMirror detects no heartbeats from a node, a node is considered as failed and resources are automatically transferred to another node.

We highly recommend configuring multiple communication paths between the nodes in the cluster. Having multiple communication networks prevents cluster partitioning, in which the nodes within each partition form their own entity. In a partitioned cluster, it is possible that nodes in each partition could allow simultaneous non-synchronized access to the same data. This can potentially lead to different views of data from different nodes.