Arm scheduling in shadowed disks

Abstract

The author describes a number of configurations and disk scheduling algorithms for shadow sets, and presents an analysis of seek time based on both a simulation and an analytic model. She focuses on the algorithm based on assigning a read request to the arm that is within the shortest seek distance of the target location. With this scheduling algorithm, shadowing five disks decreases the expected seek time for reads by 50%. For a ratio of reads to writes equal to 1.5 or higher, shadowing decreases the overall seek time by 20%.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>