Symmetric Tree Replication Protocol for Efficient Distributed Storage System

In large distributed systems, replication of data and service is needed to decrease the communication cost, increase the overall availability, avoid single server bottleneck, and increase the reliability. Tree quorum protocol is one of the replication protocols allowing very low read cost in the best case but has some drawbacks such that the number of replicas grows rapidly as the level increases and root replica becomes a bottleneck. In this paper we propose a new replication protocol called symmetric tree protocol which efficiently solves the problems. The proposed symmetric tree protocol also requires much smaller read cost than the previous protocols. We conduct cost and availability analysis of the protocols, and the proposed protocol displays comparable read availability to the tree protocol using much smaller number of nodes. It is thus effective to be applied to survival storage system.