RAM-DUR: In-Memory Deferred Update Replication

Abstract

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Many database replication protocols are based on the deferred update replication technique. In deferred update replication, transactions are executed by a single server, and certified and possibly committed by every server. Thus, servers must store a full copy of the database. This assumption is detrimental to performance since servers may not be able to cache the entire database in main memory. This paper introduces RAM-DUR, a variation of deferred update replication whereby transaction execution is in-memory only. RAM-DUR's key insight is a sophisticated distributed cache mechanism that provides high performance and strong consistency without the limitations of existing solutions (e.g., no single server must have enough memory to cache the entire database). In addition to presenting RAM-DUR, we detail its implementation, and provide an extensive analysis of its performance.