Practical Energy-Efficient Policies for Server Clusters

Power conservation has become a key design issue for many systems, for example, server clusters deployed in large data centers and web hosting facilities. Another example is satellite-based multiprocessor systems, where power management ultimately determines the lifetime of the system. The goal is to minimize the aggregate energy consumption of the whole server cluster while ensuring timely responses to client requests. Energy-efficient policies that employ a combination of dynamic voltage scaling (DVS) and turning nodes on/off have been studied under the assumption of continuous frequencies and the cubic-root rule of power-frequency relation. Many of the proposed policies strongly depend on the existence of a perfect load-balancing mechanism. In this work, we focus on the more realistic case of discrete frequencies and propose a new policy that adjusts the number of online servers based on the system load. The proposed policy is practical (e.g., eliminates the strong dependency on perfect load-balancing) and is shown to be more effective in reducing the overall power consumption.