An Algorithm for Non-Intrusive, Parallel Recovery of Replicated Data and its Correctness

The increasingly widespread use of cluster architectures has resulted in many new application scenarios for data replication. While data replication is, in principle, a well understood problem, recovery of replicated systems has not yet received enough attention. In the case of clusters, recovery procedures are particularly important since they have to keep a high level of availability even during recovery. In fact, recovery is part of the normal operations of any cluster as the cluster is expected to continue working while sites leave or join the system. The question is then how to optimize recovery so that it can be done without redundancies (that would affect the performance) and with minimal disruptions to normal operations. In this paper, we identify different performance and availability problems that are caused by recovery and propose an online recovery protocol to overcome them.