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Systems & Data Center · Intermediate

Cluster Quorum

The voting mechanism a failover cluster uses to decide whether enough nodes are communicating to keep running and avoid split-brain.

Definition

Each node and an optional witness (disk, file share or cloud) holds a vote; the cluster runs only with a majority. Dynamic quorum and dynamic witness adjust votes automatically as nodes leave.

Example

A two-node cluster adds a cloud witness so one node can survive the other's failure.

Exam tip

Even-node clusters need a witness to break ties and prevent split-brain.

Related terms