Fencing for high availability

Fencing, sometimes known as Shoot The Other Node In The Head (STONITH) sounds pretty dramatic, and at first sight it may seem odd that it is a good thing for high availability. In this recipe, we will discuss why fencing is required in all clusters, and then discuss its implementation using the scripts provided with RHEL and CentOS.

There is only one way to be sure that something is dead—that is, to kill it yourself. For a shared-storage cluster, it is considered good enough to ask something to die—but only if it is able to confirm with absolute clarity that it has indeed successfully died. The reason for this caution is that if a node is considered dead, but is in fact able to consider writing to a shared-storage ...

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