1. A system for maintaining coherency of replicated data in a distributed data processing system having a plurality of processors interconnected by a communications medium and a plurality of storage devices, each of said storage devices controlled by at least one of said plurality of processors, said replicated data being replicated on two or more of said plurality of storage devices, said system comprising: means for detecting an event occurring in said data processing system; means for initiating an update of said replicated data in response to said detected event; means for selecting one of said plurality of processors to coordinate said update of said replicated data; said selected one of said plurality of processors to coordinate said update of said replicated data including means for updating said replicated data, said means for updating causing each copy of said replicated data to become a duplicate of all other copies of said replicated data, said updating means including: means for requesting modification logs from said plurality of processors; means for receiving all requested modification logs; means for merging all received modification logs; and means for sending said merged modification logs to said plurality of processors.