Abstract: A system and method for effectuating distributed consensus among members of a processor set in a multiprocessor computing system that is effective even when only a single surviving processor is operational and is achieved through joint implementation of a virtual state machine utilizing a sequence of numbered input commands. System synchronization is achieved by having all of the processors agree on the sequence of input commands so that they execute the same virtual state machine. Input commands are numbered consecutively and the processors use a set of shared stores (e.g. disk drives) to communicate amongst themselves requests (i.e. ballots) for new state machine inputs (or commands) and state machine inputs that have already been chosen (i.e. committed commands). A consensus process is used to decide upon (or commit) each command and this consensus is achieved using a majority of known system stores rather than a majority of known processors.

Abstract: A system and method exclusively accesses a shared storage location using a shared algorithm. Competing processors follow the algorithm for reserving exclusive access to the shared storage location. Those competing processors that have not successfully reserved exclusive access honor the reservation of the successful processor and delay their own access attempts. Two critical storage blocks and two delay times are typically used during an attempt to reserve exclusive access for a processor.