A simulation model for analyzing service times in a rotational position sensing disk system

Abstract

The performance of a computer system is often directly depen dent on the performance of the disk subsystems supporting it. Therefore, we have developed a model to aid in the evaluation of disk subsystem performance, with special emphasis on the rotational position sensing (RPS) feature due to its widespread use. The model produces I/O service times broken down by device within the disk subsystem, which can be used as a basis for design and placement decisions for critical applications. The model also produces channel and device utilizations and other measures of disk performance. Data-driven, the model uses data obtained from direct measure ment of the operating system in use. Thus the analyst need not know or make assumptions about the characteristics of the existing devices in the subsystem. Validation is accomplished through direct measurement of an existing system. In a wide-range of initial applications, the model has proven to be a valuable tool for the analysis of disk subsystems.