mwang_pay (07/20/82)
DEPARTMENT OF COMPUTER SCIENCE UNIVERSITY OF WATERLOO SEMINAR ACTIVITIES SYSTEMS SEMINAR - Monday, July 26, 1982. Mr. Alfredo R. Piquer, a graduate student of this depart- ment, will speak on "A Reliable Replicated Storage Service for a Local network." TIME: 3:30 PM ROOM: M&C 5158 ABSTRACT When personal workstations are connected by a local net- work, it is often useful to have shared central storage servers that store files, user lists, etc. A method to increase the reliability of such a service is to have mul- tiple copies of the stored data, so that it can be avail- able even if some of the copies fail. We describe an efficient method to build a reliable ser- vice with multiple copies of the data. The service pro- vided is similar to a single-copy server from the client's point of view. The algorithms used are proved to have a correct behavior, even under the presence of failures of the various copies or of the communication mechanism. When no failures occur, the only overhead involved in the method is the propagation of requests to all the copies. The method does not provide a mechanism for atomic tran- sactions, although individual update operations behave atomically. The implementation of the service does not use any type of global storage, and it does not use atomic transactions. The only atomicity assumption is that a data update in one copy is atomic.