Exploiting Application Workload Characteristics to Accurately Estimate Replica Server Response Time

We revisit the problem of selecting the suitable server, among a list of replica servers, so as to optimize the response time resulting from the execution of the clients’ requests. Our proposition, presented in this paper, consists in the definition of a function estimating the response time and a method for applying it to different application workloads. The function combines the application demands for various resources (such as the CPU, the disk I/O and the network bandwidth) with the resource capabilities and availabilities on the replica servers. The main benefits of our approach include: the simplicity and the transparency, from the perspective of the clients, who don’t have to specify themselves the selection criteria, the estimation accuracy, by considering the application real needs and the current degree of resource usage, determined by concurrent applications and the flexibility, with respect to the precision with which the resource-concerned parameters are specified. The experiments we conducted show two positive results. Firstly, our estimator provides a good approximation of the real response time obtained by measurements. Secondly, the ordering of the servers according to our estimation function values, matches with high accuracy the ordering determined by the real response times.