A new approach to developing and implementing eager database replication protocols

TLDR

Database replication traditionally boosts availability and performance, yet most consistency protocols are too complex for commercial use, leading products to tolerate inconsistencies and rely on centralized approaches that negate replication benefits. The authors propose a suite of replication protocols to solve key replication problems. The protocols preserve consistency and transactional semantics by leveraging group communication primitives and relaxed isolation, eliminating deadlocks, reducing message overhead, and boosting performance. Simulations demonstrate the approach’s feasibility, flexibility in avoiding bottlenecks, and improved performance through deadlock elimination and reduced overhead.

Abstract

Database replication is traditionally seen as a way to increase the availability and performance of distributed databases. Although a large number of protocols providing data consistency and fault-tolerance have been proposed, few of these ideas have ever been used in commercial products due to their complexity and performance implications. Instead, current products allow inconsistencies and often resort to centralized approaches which eliminates some of the advantages of replication. As an alternative, we propose a suite of replication protocols that addresses the main problems related to database replication. On the one hand, our protocols maintain data consistency and the same transactional semantics found in centralized systems. On the other hand, they provide flexibility and reasonable performance. To do so, our protocols take advantage of the rich semantics of group communication primitives and the relaxed isolation guarantees provided by most databases. This allows us to eliminate the possibility of deadlocks, reduce the message overhead and increase performance. A detailed simulation study shows the feasibility of the approach and the flexibility with which different types of bottlenecks can be circumvented.