A quorum-consensus replication method for abstract data types

Replication can enhance the availability of data in distributed systems. This paper introduces a new method for managing replicated data. Unlike many methods that support replication only for uninterpreted files, this method systematically exploits type-specific properties of objects such as sets, queues, or directories to provide more effective replication. Each operation requires the cooperation of a certain number of sites for its successful completion. A quorum for an operation is any such set of sites. Necessary and sufficient constraints on quorum intersections are derived from an analysis of the data type's algebraic structure. A reconfiguration method is proposed that permits quorums to be changed dynamically. By taking advantage of type-specific properties in a general and systematic way, this method can realize a wider range of availability properties and more flexible reconfiguration than comparable replication methods.