Node fencing is a concept in computer clusters. A node fence (or I/O fence) is a virtual "fence" that separates nodes which may have access to a shared resource from nodes which must not. It may separate an active node from its backup. If the backup crosses the fence and, for example, tries to control the same disk array

Disk array

A disk array is a disk storage system which contains multiple disk drives. It is differentiated from a disk enclosure, in that an array has cache memory and advanced functionality, like RAID and virtualization.Components of a typical disk array include:...

 as the primary, a data hazard may occur. Mechanisms such as STONITH

STONITH

STONITH , sometimes called STOMITH , is a technique for fencing in computer clusters. Fencing is the isolation of a failed node so that it does not cause disruption to a cluster...

 are designed to prevent this condition.

See also Fencing (computing)

Fencing (computing)

Fencing is the process of isolating a node of a computer cluster when the former is malfunctioning. Isolating a node means ensuring that I/O can no longer be done from it. Fencing is typically done automatically, by cluster infrastructure such as shared disk file systems, in order to protect...