TOFF-2: A high-performance fault-tolerant file service

TOFF-2 is a high-performance fault-tolerant file service featuring in a new Symmetric Primary Backup (SPB) replication model. This model lets all repl icated servers in a service share the load of a traditional primary server, and minimizes the communication overhead between servers. TOFF-2 is also t otally transparent to the client machines, and any host with an NFS client implementation can use the fault-tolerant service provided by TOFF-2 withou t any modification. The clients do not have to know anything about replicat ion and server failures, since the TOFF-2 service cluster looks exactly lik e a single server over the network. The concept and design of TOFF-2 is int roduced in this article, and statistics taken from tests on a prototype imp lementation show promising results. (C) 2000 Elsevier Science Inc. All righ ts reserved.