Adaptive Disk Spin-down Policies for Mobile Computers
Fred Douglis (Email: email@example.com)
AT&T Bell Laboratories
University of Washington
This work was performed in part at the Matsushita Information
Technology Laboratory of Panasonic Technologies, Inc.
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.
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