A resource used in Microsoft clustering services - Microsoft Cluster Server (MSCS) for Microsoft Windows NT Server 4.0, Enterprise Edition, and Windows Clustering for Windows 2000 - that guarantees that data necessary for recovery is maintained consistently among all members of a cluster. The quorum resource must be a physical disk and can be owned by only one node in a cluster.
The quorum resource stores the cluster log, which is maintained by the clustering software. If a node fails and then recovers, the quorum resource is responsible for updating that node’s configuration information so that it matches all other nodes. If the nodes in a cluster cannot communicate with each other, the quorum resource determines which node can continue operating.
If the node owning the quorum resource fails, another node takes ownership of the resource. Each cluster can have only one quorum resource.