Power-efficient Server-class Performance from Arrays of Laptop Disks
Michael Lee Scott, Athanasios E. Papathanasiou · UR Research (University of Rochester) · 2004
The disk array of a server-class system can account for a significant portion of the server’s total power budget. Similar observations for mobile (e.g. laptop) systems have led to the development of power management policies that spin down the hard disk when it is idle, but these policies do not transfer well to server-class disks. On the other hand, state-of-the-art laptop disks have response times and bandwidths within a factor of 2.5 of their server class cousins, and consume less than one sixth the energy. These ratios suggest the possibility of replacing a server-class disk array with a larger array of mirrored laptop disks. By spinning up a subset of the disks proportional to the current workload, we can exploit the latency tolerance and parallelism of typical server workloads to achieve significant energy savings, with equal or better peak bandwidth. Potential savings range from 50% to 80% of the total disk energy consumption.