Effects of channel blocking on the performance of shared disk pack in a multi-computer system

Abstract

In a multi-computer environment where several computers share packs of disk drives, the architecture of the disk controller can have significant effect on the throughput of the disk pack. In a simple configuration a controller can allow access to only one disk in the pack at a time, and effectively block other channels from accessing other disks in the pack. A desirable alternative is to be able to access different disks of the same pack simultaneously from different channels. Motivated by the presence of a mixed hardware in an installation to support both configurations, an attempt is made to model each system and produce analytical and simulation results to compare their relative performances. It is predicted that under the prevalent conditions in the installation, a complete switchover to either system should not give rise to significant performance change.