A quorum device acts as a third-party arbitrator in the event where standard quorum rules might not adequately cater for node failure. A quorum device is typically used where there may be an even number of nodes in a cluster. For example, in a cluster that contains two nodes failure of the nodes to communicate can result in a split-brain issue where both nodes function as primary at the same time, which results in possible data corruption. By using a quorum device, quorum arbitration can be achieved and a selected node survives.

A quorum device is a service that ideally runs on a separate physical network to the cluster itself. It should run on a system that's not a node in the cluster. Although the quorum device can service multiple clusters at the same time, it should be the only quorum device for each cluster that it serves. Each node in the cluster is configured for the quorum device. The quorum device is installed and run as a network bound service on a system outside of the cluster network.