A Oueueing Model Of A Rotational Position Sensing Disk System

Abstract

In this paper we present a general model of disk storage systems equipped with rotational position sensing (RPS). These systems are distinguished by sector scheduling at the channel. We show that the number of revolutions spent waiting for the channel due to the RPS feature is not geometrically distributed, as was assumed in most previous models. In place of the geometric assumption we give an approximate formula for the mean and variance of the number of revolutions required, and use this formula to develop an open, single queue model representing one disk module of the multi-module system. This model is then compared to simulations and to a previously developed analytic model. Finally, we develop a closed queueing network model using the single queue model as a component, and an approximate solution method is described by which to obtain performance measurements from the closed model.