Resilient memory-resident data objects

The authors investigate the feasibility of replicated data objects consisting of several memory-resident replicas backed-up by a single append-only long maintained on disk. First, it is shown that such objects can be managed by simple variants of the most popular replication control protocols for disk-resident replicated objects. Second, under standard Markovian hypotheses, the availability of replicated objects consisting of memory-resident replicas and a single append-only log on disk are analyzed and shown that they have almost the same availability as replicated objects having all their replicas residing on disk. Using memory-resident replicas has the advantage of faster access over disk-resident replicas. The cost is an increase in recovery time to reconstruct from the log. The authors suggest several improvements that could be made to speed the recovery of the protocols. The analysis demonstrates that memory-resident replicas provide a level of fault-tolerance comparable to disk-resident replicas