Robust Object Replication in a DHT Ring

There have been a lot of studies on distributed storage systems and peer-to-peer file systems based on distributed hash tables (DHTs), in which nodes have global unique identifiers generated by a hash function. Since such distributed systems are built on top of a heterogeneous and unreliable infrastructure, replication techniques are often used to improve object availability. However, typical consecutive replication technique provided by DHTs can encounter replication failures caused by storage imbalance due to some reasons such as storage heterogeneity, various file size distribution, or insert rush to some ID regions. In this project, we develop heuristics to provide robust object replication by exploring more nodes than the traditional replication technique. According to the simulation result conducted on PlanetSim, the suggested heuristics significantly diminish replication failure rate with a little overhead. In addition, we present how to maintain replicas with the suggested heuristics in churn situations which is pretty common in wide-area distributed systems.