Understanding the Role of Atomic Transactions and Group Communications in Implementing Persistent Replicated Objects

A widely used computational model for constructing fault-tolerant distributed applications employs atomic transactions for controlling operations on persistent objects. There has been considerable work on data replication techniques for increasing the availability of persistent data that is manipulated under the control of transactions. Process groups with ordered group communications has also emerged as a model for building available distributed applications. High service availability can be achieved by replicating the service state on multiple processes managed by a group communication infrastructure. These two models are often seen as rivals. This paper explores the role of these models in building fault-tolerant distributed applications. The paper develops a general model of distributed persistent objects and investigates how such objects can be replicated for availability using a system that supports only: (i) transactions; and (ii) process groups. A comparative evaluation shows h..