🚀 go-pugleaf

               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.