The availability of quorum systems

A quorum system is a collection of sets (quorums) every two of which intersect. Quorum systems have been used for many applications in the area of distributed systems, including mutual exclusion, data replication, and dissemination of information. In this paper we study the failure probabilities of quorum systems and in particular of nondominated coteries (NDC). We characterize NDC’s in terms of the failure probability, and prove that any NDC has availability that falls between that of a singleton and a majority consensus. We show conditions for weighted voting schemes to provide asymptotically high availability, and we analyze the availability of several other known quorum systems.