Date: 11 Oct 2005

Competitive analysis of on-line disk scheduling

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We give a detailed competitive analysis of a popular on-line disk scheduling algorithm, namely, LOOK. Our analysis yields a tight competitive ratio for the LOOK algorithm. By comparing and contrasting the competitive ratio of LOOK with the lower bounds of FCFS and SSTF (which are equally popular in disk scheduling), our results provide strong evidence to suggest that when the workload of disk access is heavy, LOOK outperforms SSTF and FCFS. As a by-product, our analysis also reveals (quantitatively) the role played by the degree of look-ahead in disk scheduling.