A replicated Unix file system

An implementation of a replicated Unix file system for use via the NFS protocol is reported. The replication method is intended to support the following goals: when used via NFS, the system should provide the same semantics as an unreplicated NFS server, and it should be usable with whatever NFS client code exists at the client machine; the system should not depend on proprietary information; the system should continue to provide service even when one replica is crashed or inaccessible, but have only two copies of each file; the system should perform as reliably as a single, unreplicated NFS server; and the system should provide response time comparable to that provided by a single NFS server. In particular, the delay observed by the client in doing a read or write should be no greater than with a single server. The system organization, replication method, performance, and Unix issues are discussed