Topology Sensitive Replica Selection

As the disks typically found in personal computers grow larger, protecting data by replicating it on a collection of "peer" systems rather than on dedicated high performance storage systems can provide comparable reliability and availability guarantees but at reduced cost and complexity. In order to be adopted, peer-to-peer storage systems must be able to replicate data on hosts that are trusted, secure, and available. However, recent research has shown that the traditional model, where nodes are assumed to have identical levels of trust, to behave independently, and to have similar failure modes, is over simplified. Thus, there is a need for a mechanism that automatically and efficiently selects replica nodes from a large number of available hosts with varying capabilities and trust levels. In this paper we present an algorithm to handle replica node selection either for new replica groups or to replace failed replicas in a peer-to-peer storage system. We show through simulation that our algorithm maintains the node inter-connection topology minimizing the cost of recovery from a failed replica, measured by the number of nodes affected by the failure and the number of inter-node messages