Partition-based Profit Optimisation for Multi-class Requests in Clusters of Servers

This paper investigates profit optimisation by the partitioning of server pools. Different types of web requests are considered in this paper: best-effort requests and multi-class QoS-demanding requests. Each request is associated with a certain amount of revenue. The system earns associated revenue when completing a best effort request, while the revenue earned for serving a QoS-demanding request depends on the degree of satisfaction. The complete server pool is divided into two clusters of servers, each dedicated to serving one type of request. The total profits accrued when serving these requests are mathematically modelled in this paper. The optimisation equations for the pool partitioning have also been constructed so that the maximum profit can be achieved. An optimal server switching policy is also developed. The server switching policy is optimal in the sense that the maximum profit can be maintained by switching servers from one partition to the other. Costs involved in server switching are factored into the switching model. Supportive experimentation based on simulation have been conducted and the results verify the effectiveness of the pool partitioning policy and the server switching policy developed in this paper.