Redhat Cluster - Fencing, what is it about?

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░ +Suwardi-Wed 10/Aug/2016 09:40 +Centenial Tower 12th fl+

What is Fencing? Fencing is a statement from cluster to cut off / disconnect a node from cluster. A node that to be disconnected, it will be cut off from share storage device connection. This function is handled by fenced daemon. 



Before fenced daemon handle a node disconnection, there is a cman decided which node failed. After got a confirmation of node failed from cman, then fenced daemon disconnects that node and cut off the I/O of share storage to the node. Other cluster component for example DLM and GFS will wait to do their job until fenced daemon finish disconnected node.

Fence devices is an engine which do failover / moving a service from failed node to standby node. It's depend hardware what we'll use on cluster. If your hardware is uncommon and not supported by Redhat, you can user IPMI Lan. Common hardware support IPMI Lan protocol. If you using Fujitsu hardware, you can user "Fujitsu Siemens RemoteView Service Board". This fencing device should be defined in the cluster configuration to do fencing function on your cluster enviroment.