Consistency of Replicated Datasets in Grid Computing

Data replication is a well-known technique used in distributed systems in order to improve fault tolerance and make data access faster. Several copies of a dataset are created and placed at different nodes, so that users can access the replica closest to them, and at the same time the data access load is distributed among the replicas. In today’s Grid middleware solutions, data management services allow users to replicate datasets (i.e., flat files or databases) among storage elements within a Grid, but replicas are often considered read-only because of the absence of mechanisms able to propagate updates and enforce replica consistency. In this entry we analyze the replica consistency problem and provide hints for the development of a Replica Consistency Service, highlighting the main issues and pros and cons of several approaches.