Disk Response Time Measurements

This paper describes response time measurements made by inserting tracing code in the UNIX® System device driver for the Digital Equipment Corporation TM (DEC**) RA81 disks attached to a DEC UDA50 controller. The goals and methodology of the measurements are described. Detailed analysis of data derived from the measurements is provided, and some conclusions are drawn about the effect of UNIX file system mechanisms on response times as seen by user processes