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The ADvanced Systems Laboratory (ADSL)
Publication abstract

Robust, Portable I/O Scheduling with the Disk Mimic

Florentina I. Popovici, Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau,

Department of Computer Sciences, University of Wisconsin-Madison


We propose a new approach for I/O scheduling that performs on-line simulation of the underlying disk. When simulation is integrated within a system, three key challenges must be addressed: first, the simulator must be portable across the full range of devices; second, all configuration must be automatic; third, the computation and memory overheads must be low. Our simulator, the Disk Mimic, achieves these goals by building a table-based model of the disk as it observes the times for previous requests. We show that a shortest-mimicked-time-first (SMTF) scheduler performs nearly as well as an approach with perfect knowledge of the underlying device and that it is superior to traditional scheduling algorithms such as C-LOOK and SSTF; our results hold as the seek and rotational characteristics of the disk are varied.

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