Protector: A Probabilistic Failure Detector for Cost-Effective Peer-to-Peer Storage
Maintaining a given level of data redundancy is a fundamental requirement of Peer-To-Peer (P2P) storage systems - to ensure desired data availability, additional replicas must be created when peers fail. Since the majority of failures in P2P networks are transient (i.e., peers return with data intact), an intelligent system can reduce significant replication costs by not replicating data following transient failures. Reliably distinguishing permanent and transient failures, however, is a challenging task, because peers are unresponsive to probes in both cases. In this paper, the authors propose Protector, an algorithm that enables efficient replication policies by estimating the number of "Remaining replicas" for each object, including those temporarily unavailable due to transient failures.