A quorum device is a shared storage device or quorum server that is shared by two or more nodes and that contributes votes that are used to establish a quorum. The cluster can operate only when a quorum of votes is available. The quorum device is used when a cluster becomes partitioned into separate sets of nodes to establish which set of nodes constitutes the new cluster.
Both cluster nodes and quorum devices vote to form quorum. By default, cluster nodes acquire a quorum vote count of one when they boot and become cluster members. Nodes can have a vote count of zero when the node is being installed, or when an administrator has placed a node into the maintenance state.
Quorum devices acquire quorum vote counts that are based on the number of node connections to the device. When you set up a quorum device, it acquires a maximum vote count of N-1 where N is the number of connected votes to the quorum device. For example, a quorum device that is connected to two nodes with nonzero vote counts has a quorum count of one (two minus one).