1. In a server cluster having plural server nodes implementing a server tier in a client-server computing architecture, a quorum determination system for determining which of two or more partitioned server subgroups running different cluster applications on behalf of cluster application clients has a quorum, comprising: priority determining logic implemented by one or more of said server nodes for determining relative priorities of said subgroups; said relative priorities being determined by policy rules that evaluate server node application state information following a cluster partitioning that produces said subgroups, said application state information including application criticality information and application client connectivity information collected during operation of said cluster prior to said cluster partitioning; said application criticality information and said application client connectivity information allowing said relative priorities to be determined according to relative priorities of cluster applications run by said subgroups and relative numbers of cluster application clients connected to said subgroups such that a relative importance of each subgroup may be determined based on the cluster applications each subgroup runs and the cluster application clients each subgroup serves; and quorum request logic implemented by one or more of said server nodes for requesting a quorum based on said relative priorities so that a quorum will only be awarded to a subgroup having a highest relative subgroup priority.