Scalable database replication through dynamic multiversioning

We scale the database back-end in dynamic content cluster servers by distributing read-only transactions on a set of lightweight database replicas while maintaining 1copy-serializability. This is contrary to conventional wisdom in replicated databases which says that one could have either 1-copy serializability or scalability, but not both. The key to scaling is a novel integrated fine-grained concurrency control and data replication algorithm called Dynamic Multiversioning that provides fine-grained distributed concurrency control at the level of a memory page across a database cluster. We exploit the different distributed data versions that naturally come about as a result of asynchronous data replication in order to increase concurrency by running conflicting transactions in parallel on different replicas. At the same time, the serialization order is determined using fine-grained concurrency control at a master database and enforced through a version-aware scheduling technique. Our technique does not put any crucial data in the scheduler, which permits easy reconfiguration, without loss of data, in the case of single-node failures of any node in the system. Our measurements show near-linear scaling up to 8 databases for the browsing, shopping and even for the write-heavy ordering workload of the industry-standard e-commerce TPC-W benchmark.