Bolt-on global consistency for the cloud

Abstract

Web services that enable users in multiple regions to collaborate can increase availability and decrease latency by replicating data across data centers. If such a service spreads its data across multiple cloud providers—for the associated performance, cost, and reliability benefits—it cannot rely on cloud providers to keep the data globally consistent. Therefore, in this paper, we present an alternate approach to realizing global consistency in the cloud, which relies on cloud providers to only offer a strongly consistent storage service within each data center. A client library then accesses replicas stored in different data stores in a manner that preserves global consistency. To do so, our key contribution lies in rethinking the Paxos replication protocol to account for the limited interface offered by cloud storage. Compared to approaches not tailored for use in the cloud, our system CRIC can either halve median write latency or lower cost by up to 60%.