# Amortized analysis of some disk scheduling algorithms: SSTF, SCAN, and*N*-StepSCAN

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DOI: 10.1007/BF01994839

- Cite this article as:
- Chen, TS., Yang, WP. & Lee, R.C.T. BIT (1992) 32: 546. doi:10.1007/BF01994839

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## Abstract

The amortized analysis is a useful tool for analyzing the time-complexity of performing a sequence of operations. The disk scheduling problem involves a sequence of requests in general. In this paper, the performances of representative disk scheduling algorithms,*SSTF, SCAN*, and*N-StepSCAN*, are analyzed in the amortized sense. A lower bound of the amortized complexity for the disk scheduling problem is also derived. According to our analysis,*SCAN* is not only better than*SSTF* and*N-StepSCAN*, but also an optimal algorithm. Various authors have studied the disk scheduling problem based on some probability models and concluded that the most acceptable performance is obtained from*SCAN*. Our result therefore supports their conclusion.