Freshness-based edge-write architecture for data replication over the internet

Abstract

We propose an Edge-write architecture which replicates and distributes data in the wide area network. Our system performs eager update propagation for update requests for the corresponding secondary server, whereas it lazily propagates updates from other secondary servers. Our architecture resolves consistency problems caused by read/update decoupling in the conventional lazy update propagationbased system. Although there is possibility for version difference to be occurred among several replicas, our concurrency mechanism easily detects such temporal inconsistency and keeps all replica nodes to be eventually consistent. Our system also improves overall scalability by alleviating the performance bottleneck at the primary server in compensation for increased but bounded response time. Such relaxed consistency management enables a read request to choose whether to read the replicated data immediately or to refresh it. We use the age of a local data copy as the freshness factor so that a secondary server can make a decision for freshness control independently. As a result, our freshness-controlled edge-write architecture benefits by adjusting a tradeoff between the response time and the correctness of data.