Minimizing mean seek distance in mirrored disk systems by cylinder remapping

Cylinder remapping is advocated as a technique for reducing mean seek distance in both single and mirrored disk systems. Cylinder request streams are measured and found to exhibit strong Markovian dependence. Expressions for mean seek distance that incorporate this dependence are developed for both the single disk and mirrored disk systems. These expressions are used as energy functions in simulated annealing and geometric annealing optimization routines in order to find permutations that deliver reduced mean seek distances under stochastically equivalent workloads. In general, the optimal permutations for the two disks in the mirrored system are seen to be non-identical. © 1994