Monitoring Fencing Devices

Just like any other resource, the STONITH class agents also support the monitor operation which is used for checking the status.

	Monitoring STONITH Resources
Monitoring STONITH resources is strongly recommended. Monitor them regularly, yet sparingly.

Fencing devices are an indispensable part of an HA cluster, but the less you need to exercise them, the better. Power management equipment is known to be rather fragile on the communication side. Some devices give up if there was too much broadcast traffic on the wire. Some cannot handle more than ten or so connections per minute. Some get confused or depressed if two clients try to connect at the same time. Most cannot handle more than one session at the time.

So checking the fencing devices once every couple of hours should be enough in most cases. The probability that within those few hours there will be a need for a fencing operation and that the power switch would fail is usually low.

For detailed information on how to configure monitor operations, refer to Adding or Modifying Meta and Instance Attributes for the GUI approach or to Section 5.8, “Configuring Resource Monitoring” for the command line approach.