A PID-Controlled Power Manager for Energy Efficient Web Clusters

Large data centers using high-end processors operating continuously around the clock are major energy consumers. Long periods of idling due to low workload will cause a waste in energy because the processors are active but not doing any useful work. A cluster of low-end embedded processors could continuously match its computational capacity with the workload at a much finer granularity than a server-grade processor by changing the power states of the CPUs. This paper introduces a framework simulating a system level power manager for many-core clusters targeting server cards used in warehouse-sized data centers. The power management system uses sleep states to switch on or off processing elements in a cluster of low power boards to match the capacity of the whole system with the workload, and thus save energy. A PID-controller is implemented in the system, a component already well known with established methods in the industrial control domain. We intend to use this component to effectively determine the number of active processing elements in the used many-core cluster. The proposed power manager can save up to 62 percent in energy compared to a system which only uses dynamic voltage and frequency scaling as power management.