Fencing is an important cluster task. It isolates a computer cluster node when the node misbehaves in order to protect the shared cluster resources and prevent cluster disruption. If you do not configure fencing, a misbehaving computer cluster node can corrupt the cluster data. This is why it is necessary to exclude the problematic cluster node from cluster configuration immediately. Corosync version 2 fencing implements some additional configurable parameters that can be applied to allow fencing configuration in a two-node cluster configuration and ensure normal operation of such a cluster. The details of this are described in Chapter 14, Two-node Cluster Considerations on CentOS 7.

In Pacemaker, fencing is called STONITH. STONITH is a fencing technique that stands for Shoot The Other Node In The Head. STONITH fences failed cluster nodes by rebooting or powering the node off.

The node fencing cluster feature is provided by fencing agents. Fencing agents are scripts that get executed...