CaLibRe: A Better Consistency-Latency Tradeoff for Quorum Based Replication Systems

In Multi-writer, Multi-reader systems, data consistency is ensured by the number of replica nodes contacted during read and write operations. Contacting a sufficient number of nodes in order to ensure data consistency comes with a communication cost and a risk to data availability. In this paper, we describe an enhancement of a consistency protocol called LibRe, which ensures consistency by contacting a minimum number of replica nodes. Porting the idea of achieving consistent reads with the help of a registry information from the original protocol, the enhancement integrate and distribute the registry inside the storage system in order to achieve better performance. We propose an initial implementation of the model inside the Cassandra distributed data store and the performance of LibRe incarnation is benchmarked against Cassandra’s native consistency options ONE, ALL and QUORUM. The test results prove that using LibRe protocol, an application would experience a similar number of stale reads compared to strong consistency options offered by Cassandra, while achieving lower latency and similar availability.