Optimal Policy of a Server System with Replication Buffering Relay Method

Recently, a replication buffering relay method has been used for a server system. The replication buffering relay method replicates data synchronously and enables a fast system migration when a disaster has occurred in the main site. We have already discussed the reliability model in the server system with the replication buffering relay method. But when a disaster has occurred in the main site, there is a problem that the response time of accessing the data in buffering relay unit is longer than that of accessing the data in the backup site. In this paper, we discuss the optimal policy to reduce the overhead of accessing the updated data in buffering relay unit. That is, we derive the probability of accessing updated data in buffering relay unit. Further, we calculate the cost effectiveness and discuss an optimal replication interval to minimize it. Finally, numerical examples are given.