Quorum-based Synchronization Protocol of Object Replicas in Scalable Distributed Systems

Information systems are getting scalable like cloud computing systems and peer-to-peer (P2P) overlay networks. In information systems, resource objects like databases are distributed and replicated in order to increase the performance, reliability, and availability. In this paper, we consider multimedia objects like movies which are characterized in terms of not only data structure like part of relations of objects but also quality of service (QoS) like frame rate. A pair of replicas may have the same content but different level of QoS. Thus, kinds of replicas of a multimedia object are distributed. Replicas of an object are partially ordered in terms of newness of contents and QoS parameters, while replicas are just totally ordered in traditional quorum theories. We classify operations on an object to three types I, O, IO types of operations with respect to whether or not data and QoS are read and written in the object. We define a quorum for each type of operation. We discuss how to synchronize multiple replicas on the basis of the quorum concept in scalable distributed systems.