 
Summary: Minimizing Stall Time in Single and Parallel Disk Systems
Susanne Albers Naveen Garg y Stefano Leonardi z
Abstract
We study integrated prefetching and caching problems following
the work of Cao et. al. [3] and Kimbrel and Karlin [13]. Cao et. al.
and Kimbrel and Karlin gave approximation algorithms for mini
mizing the total elapsed time in single and parallel disk settings.
The total elapsed time is the sum of the processor stall times and
the length of the request sequence to be served.
We show that an optimum prefetching/caching schedule for a
single disk problem can be computed in polynomial time, thereby
settling an open question by Kimbrel and Karlin. For the parallel
disk problem we give an approximation algorithm for minimizing
stall time. Stall time is an important and harder to approximate
measure for this problem. All of our algorithms are based on a
new approach which involves formulating the prefetching/caching
problems as integer programs.
1 Introduction
Prefetching and caching are powerful tools for increasing the per
formance of file and data base systems. In prefetching, memory
