Log′ version vector: Logging version vectors concisely in dynamic replication

In a replication system, version vectors are logged with replicas to detect conflicts among operations. Dynamic replications where replicas are frequently created and destroyed suffer from expensive logging overhead caused by inactive entries of version vectors. Although the rigmarole of pruning vectors can delete inactive entries, the vectors may be incompatible without additional information, which also causes another overhead. This paper proposes a novel version vector called log′ (log-prime) consisting of only three entries. By encoding based on the characteristics of prime numbers, log′ version vectors of fixed size can be logged concisely with no pruning technique at a little sacrifice in accuracy. Simulation studies show that log′ version vectors are accurate enough to detect almost all conflicts in the replication systems where all replicas are fully synchronizing.