Cluster Fence

AN!Wiki :: Cluster Fence

A fence in clustering is a device and/or program that a node can use to shut down or otherwise disable another node or nodes in a cluster.

This is critical in clustering because, on occassion, nodes will lose connection with each other. When this happens, two or more nodes will think that the other node is down and begin to take over control of shared services. If this service is something like a file system, data corruption becomes very likely. To prevent this, a fence is used to "kill" the other node. When both nodes are still up, then the fastest node survives and the slower node dies.

To picture this, imagine two people in a dual. The faster person will live because the slower person died before they could pull their trigger.

In this way, the surving node can take over cluster services and be confident that nothing else is trying to use them at the same time.

 

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