Conserving disk energy in network servers

In this paper we study four approaches to conserving disk energy in high-performance network servers. The first approach is to leverage the extensive work on laptop disks and power disks down during periods of idleness. The second approach is to replace high-performance disks with a set of lower power disks that can achieve the same performance and reliability. The third approach is to combine high-performance and laptop disks, such that only one of these two sets of disks is powered on at a time. This approach requires the mirroring (and coherence) of all disk data on the two sets of disks. Finally, the fourth approach is to use multi-speed disks, such that each disk is slowed down for lower energy consumption during periods of light load. We demonstrate that the fourth approach is the only one that can actually provide energy savings for network servers. In fact, our results for Web and proxy servers show that the fourth approach can provide energy savings of up to 23%, in comparison to conventional servers, without any degradation in server performance.