Reliability Characteristics of a Server System with Asynchronous and Synchronous Replications

Abstract

Recently, replication mechanisms for a disaster recovery have been widely used for the server system. This paper considers the reliability in server systems with synchronous and asynchronous replications for the disaster recovery. We formulate two stochastic models of server systems with synchronous and with asynchronous replications: In synchronous replication, the server transmits the database content to a backup site as soon as a main site updates the storage database. In asynchronous replication, the server transmits the database content to a backup site after a constant time. We derive the expected number of the replication and the probability of migrating routine work to the backup site and the probability of the system down. Further, in asynchronous model, we calculate the cost effectiveness and discuss an optimal policy to minimize it. Finally, in asynchronous and in synchronous models, numerical examples are given to compare the performance of them.