Boosting Database Replication Scalability through Partial Replication and 1-Copy-Snapshot-Isolation

Databases have become a crucial component in modern information systems. At the same time, they have become the main bottleneck in most systems. Database replication protocols have been proposed to solve the scalability problem by scaling out in a cluster of sites. Current techniques have attained some degree of scalability, however there are two main limitations to existing approaches. Firstly, most solutions adopt a full replication model where all sites store a full copy of the database. The coordination overhead imposed by keeping all replicas consistent allows such approaches to achieve only medium scalability. Secondly, most replication protocols rely on the traditional consistency criterion, 1-copy-serializability, which limits concurrency, and thus scalability of the system. In this paper, we first analyze analytically the performance gains that can be achieved by various partial replication configurations, i.e., configurations where not all sites store all data. From there, we derive a partial replication protocol that provides 1-copy-snapshot isolation as correctness criterion. We have evaluated the protocol with TPC-W and the results show better scalability than full replication.