Energy-Efficient Server Clusters

This paper evaluates five policies for cluster-wide power management in server farms. The policies employ various combinations of dynamic voltage scaling and node vary-on/vary-off (VOVO) to reduce the aggregate power consumption of a server cluster during periods of reduced workload. We evaluate the policies using a validated simulator that calculates the energy usage and response times of a Web server cluster serving traces culled from real-life Web server workloads.Our results show that a relatively simple policy of independent dynamic voltage scaling on each server node can achieve savings ranging up to 29% and is competitive with more complex schemes for some workloads. A policy that brings nodes online and takes them offline depending on the workload intensity also produces significant savings up to 42%. The largest savings are obtained by using a coordinated voltage scaling policy in conjunction with VOVO. This policy provides up to 18% more savings than just using VOVO in isolation. All five policies maintain server response times within acceptable norms.