Fencing is an automated means of isolating a node that appears to be malfunctioning, used to protect the integrity of the DRBD volumes. In a test deployment of a Control Center HA cluster, fencing is not necessary. However, on production HA clusters, fencing is a critical consideration.
Work with your IT department to implement the best fencing solution for your infrastructure. Employ a technique that ensures that a failed node in the cluster is completely stopped to avoid application conflicts or conflicts with the cluster management software.
When fencing is employed in the HA cluster, use two NICs per node.
- Ensure that all components are deployed.
- Verify operation of the application that Control Center is managing.
- In a controlled scenario, confirm basic cluster failover.
If a fencing method is not defined, when the cluster attempts to fail over to the backup node, the following error results:
no method defined
Place the fencing device on the public network. (Passing heartbeat communication through a private network interface is not recommended. Doing so requires a complex fencing system that is prone to issues. For more information, see Quorum Disk documentation on the Red Hat website.)
Using a public network interface enables a healthy node to fence the unhealthy node, and prevents the unhealthy node from fencing the healthy node. If heartbeat communications pass through the public network and the link for a node goes down, the node with the down public network link cannot communicate with the fencing device.