Re:GRIDiT — Coordinating distributed update transactions on replicated data in the Grid

The recent proliferation of Grid environments for eScience applications led to common computing infrastructures with nearly unlimited storage capabilities. In terms of data management, the Grid allows keeping a large number of replicas of data objects to allow for a high degree of availability, reliability and performance. Due to the particular characteristics of the Grid, especially due to the absence of a global coordinator, dealing with many updateable replicas per data object urgently requires new protocols for the synchronization of updates and their subsequent propagation. Currently there is no protocol which can be seamlessly applied to a data Grid environment without impacting correctness and/or overall performance. In this paper we address the problem of replication in the Data Grid in the presence of updates. We have designed the Re:GRIDiT protocol that focuses on the correct synchronization of updates to several replicas in the Grid in a completely distributed way, extending well-established database replication techniques. Globally correct execution is provided by communication between transactions and sites. Re:GRIDiT takes into account the special characteristics of eScience applications such as the distinction between mutable objects, that can be updated by users and immutable objects. Finally, we provide a detailed evaluation of the performance of the Re:GRIDiT protocol when being applied at Grid scale.