PREFiguRE

Abstract

Low disk drive utilization suggests that placing the drive into a power saving mode during idle times may decrease power consumption. We present PREFiguRE, a robust framework that aims at harvesting future idle intervals for power savings while meeting strict quality constraints: first, it contains potential delays in serving IO requests that occur during power savings since the time to bring up the disk is not negligible, and second, it ensures that the power saving mechanism is triggered a few times only, such that the disk wear-out due to powering up and down does not compromise the disk’s lifetime. PREFiguRE is based on an analytic methodology that uses the histogram of idle times to determine schedules for power saving modes as a function of the preceding constraints. PREFiguRE facilitates analysis for the evaluation of the trade-offs between power savings and quality targets for the current workload. Extensive experimentation on a set of enterprise storage traces illustrates PREFiguRE’s effectiveness to consistently achieve high power savings without undermining disk reliability and performance.