Preventive multi-master replication in a cluster of autonomous databases

Abstract

We consider the use of a cluster of PC servers for Application Service Providers where applications and databases must remain autonomous. We use data replication to improve data availability and query load balancing (and thus performance). However, replicating databases at several nodes can create consistency problems, which need to be managed through special protocols. In this paper, we present a lazy preventive data replication solution that assures strong consistency without the constraints of eager replication. We first present a peer-to peer cluster architecture in which we identify the replication manager. Cluster nodes can support autonomous, heterogeneous databases that are considered as black boxes. Then we present the multi-master refresher algorithm and show all system components necessary for implementation. Next we describe our prototype on a cluster of 8 nodes and experimental results that show that our algorithm scales-tip and introduces a negligible loss of data freshness (almost equal to mutual consistency). © Springer-Verlag 2003.