Robust, Portable I/O Scheduling with the Disk Mimic
Florentina I. Popovici, Andrea Carol Arpaci-Dusseau, Remzi H. Arpaci-Dusseau · 2003
We propose a new approach for I/O scheduling that per-forms on-line simulation of the underlying disk. When simulation is integrated within a system, three key chal-lenges must be addressed: rst, the simulator must be portable across the full range of devices; second, all con-guration 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-rst (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 ro-tational characteristics of the disk are varied. 1