Project Management

PowerNap: Eliminating Server Idle Power

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Executive Summary

Data center power consumption is undergoing an alarming acceleration. By 2011, U.S. data centers will consume 100 billion kWh at a cost of $7.4 billion per year. Research proves that much of this energy is wasted in idle systems. In typical deployments, server utilization is below 30%, but idle servers still consume 60% of their peak power draw confounding simple energy-conservation approaches. The paper presents PowerNap, an energy-conservation approach where the entire system transitions rapidly between a high-performance active state and a near-zero-power idle state in response to instantaneous load. Rather than requiring fine-grained power-performance states and complex load-proportional operation from each system component, PowerNap instead calls for minimizing idle power and transition time, which are simpler optimization goals. Based on the PowerNap concept, requirements and outline mechanisms to eliminate idle power waste in enterprise blade servers, were developed. An analytic model was constructed to demonstrate that, for typical server workloads, PowerNap far exceeds DVFS's power savings potential with better response time. Because PowerNap operates in low efficiency regions of current blade center power supplies, the Redundant Array for Inexpensive Load Sharing (RAILS), a power provisioning approach that provides high conversion efficiency across the entire range of Power-Nap's power demands was also introduced. Using utilization traces collected from enterprise-scale commercial deployments, it is demonstrated that, together, PowerNap and RAILS, reduce average server power consumption by 74%.

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