Adaptive Disk Spin-down Policies for Mobile Computers
Fred Douglis (Email: douglis@research.att.com)
AT&T Bell Laboratories
P. Krishnan
Brown University
Brian Bershad
University of Washington
This work was performed in part at the Matsushita Information
Technology Laboratory of Panasonic Technologies, Inc.
Abstract
Mobile computers typically spin down their hard disk after a fixed
period of inactivity. If this threshold is too long, the disk wastes
energy; if it is too short, the delay due to spinning the disk up
again frustrates the user. Usage patterns change over time, so a
single fixed threshold may not be appropriate at all times. Also,
different users may have varying priorities with respect to trading
off energy conservation against performance. We describe a method for
varying the spin-down threshold dynamically by adapting to the user's
access patterns and priorities. Adaptive spin-down can in some
circumstances reduce by up to 50 the number of disk spin-ups that are
deemed by the user to be inconvenient, while only moderately
increasing energy consumption.
Download the full text of this paper in
ASCII (46,031 bytes) and
POSTSCRIPT (438,140 bytes) form.
To Become a USENIX Member, please see our
Membership Information.