A replicated state machine with N replica servers may be configured to tolerate a count of F faults. A first operation (of a first ordering type) executes when a first quorum of correctly functioning replicas is available. A second operation (also of the first operation type) executes when a second quorum...http://www.google.com/patents/US8135987?utm_source=gb-gplus-sharePatent US8135987 - Collection ordering for replicated state machines
