Distributed versioning: Consistent replication for scaling back-end databases of dynamic content web sites

Abstract. Dynamic content Web sites consist of a front-end Web server, an ap-plication server and a back-end database. In this paper we introduce distributed versioning, a new method for scaling the back-end database through replication. Distributed versioning provides both the consistency guarantees of eager repli-cation and the scaling properties of lazy replication. It does so by combining a novel concurrency control method based on explicit versions with conflict-aware query scheduling that reduces the number of lock conflicts. We evaluate distributed versioning using three dynamic content applications: the TPC-W e-commerce benchmark with its three workload mixes, an auction site benchmark, and a bulletin board benchmark. We demonstrate that distributed versioning scales better than previous methods that provide consistency. Further-more, we demonstrate that the benefits of relaxing consistency are limited, except for the conflict-heavy TPC-W ordering mix.