Fine-grained consistency for geo-replicated systems

To deliver fast responses to users worldwide, major Internet providers rely on geo-replication to serve requests at data centers close to users. This deployment leads to a fundamental tension between improving system performance and reducing costly cross-site coordination for maintaining service properties such as state convergence and invariant preservation. Previous proposals for managing this trade-off resorted to coarse-grained operations labeling or coordination strategies that were oblivious to the frequency of operations. In this paper, we present a novel fine-grained consistency definition, Partial Order-Restrictions consistency (or short, PoR consistency), generalizing the trade-off between performance and the amount of coordination paid to restrict the ordering of certain operations. To offer efficient PoR consistent replication, we implement Olisipo, a coordination service assigning different coordination policies to various restrictions by taking into account the relative frequency of the confined operations. Our experimental results show that PoR consistency significantly outperforms a state-of-the-art solution (RedBlue consistency) on a 3-data center RUBiS benchmark.