Validation of a trace-driven CDC 6400 simulation

ABSTRACT

A computer center typically faces questions of how to deal with a growing load in the face of tight financial constraints and with the need for lead time for planning ways to meet the demand. The needs may be met by altering the equipment configuration, changing priority algorithms and other features of the operating system, controlling the time scheduling of various classes of job load, or perhaps shifting load from one machine to another if the center is large enough to have such a capability. It is often difficult to gather enough data and insight to show the direction these changes should go and to support the decision to do so. One useful set of tools is provided by simulation backed up by measurements required for validation. However, it is all too common to find that fear of interruptions of the computing center's service to user, combined with an overworked systems programming staff, prevents insertion of the desired measurement probes into the operating system. Then one is restricted to measures that can be derived from the normal accounting log, or "Dayfile", and to software probes that can be injected in the guise of user's programs. In spite of these limitations, useful results can be obtained, and this paper describes validation of a simulation model of a multiprogramming system, the Control Data 6400, making use of these restricted measurements.

References

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