Quorum arbitrator for a high availability system

Some clustering products such as Microsoft's Cluster Server (MSCS) utilize a quorum resource in order to maintain data integrity and cluster unity among the nodes of a cluster. In such products, the quorum resource provides physical storage that is accessible by every node of a cluster and persistent arbitration between the nodes of the clusters. In other words, the quorum resource provides a mechanism which grants ownership of the quorum resource to a single node of the cluster and defends the granted ownership from requests to gain ownership of the quorum resource from other nodes of the cluster. A computer system operable to provide nodes of a cluster with a quorum resource includes a network interface controller, a mass storage device, a processor, and memory. The network interface controller is operable to send messages to the nodes via a network and receive messages from the nodes via the network. The mass storage device includes storage that is used to implement the quorum resource and that is accessible by the nodes via the network interface controller. The processor is operably coupled to the network interface controller and the mass storage device. The memory is operably coupled to the processor and includes instructions, which when executed by the processor, cause the processor to process a first message requesting ownership of the quorum resource that is received from a first node of the cluster via the network interface controller. Furthermore, the instructions cause the processor to determine whether the first node already owns the quorum resource in response to receiving the first message. Moreover, the instructions cause the processor to determine whether a second message requesting ownership of the quorum resource is received from a second node of the cluster within a predetermined time period of receiving the first message it the first node does not already own the quorum resource. The instructions cause the processor to grant ownership of the quorum resource to the first node if the second message is not received within the predetermined time period.