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Adaptive Disk Spin-down Policies for Mobile Computers

Fred Douglis (Email:
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.


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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