Early experiences in evaluating the parallel disk model with the ViC∗ implementation

Abstract

Although several algorithms have been developed for the Parallel Disk Model (PDM), few have been implemented. Consequently, little has been known about the accuracy of the PDM in measuring I/O time and total running time to perform an out-of-core computation. This paper analyzes timing results on multiple-disk platforms for two PDM algorithms, out-of-core radix sort and BMMC permutations, to determine the strengths and weaknesses of the PDM. The results indicate the following. First, good PDM algorithms are usually not I/O bound. Second, of the four PDM parameters, one (problem size) is a good indicator of I/O time and running time, one (memory size) is a good indicator of I/O time but not necessarily running time, and the other two (block size and number of disks) do not necessarily indicate either I/O or running time. Third, because PDM algorithms tend not to be I/O bound, using asynchronous I/O can reduce I/O wait times significantly. The software interface to the PDM is part of the ViC ∗ run-time library. The interface is a set of wrappers that are designed to be both efficient and portable across several underlying file systems and target machines.