A simulation model to measure direct access storage device (DASD) performance

With the vast amounts of data being collected, analyzed and stored for today's information highway, the type and quantity of computer equipment storage media has become critical to the cost of operating a computer data service center. Processor storage is obviously the most desirable medium from a performance perspective, however, it is also the most costly. The other extreme is off-line storage such as a tape cartridge system which is the most inexpensive method but leaves much to be desired with respect to user response time. A reasonable alternative is DASD. In fact, in many installations the "DASD farm" is comparable in cost to the Central Processing Unit (CPU) configuration. The Department of Defense (DOD) is in the process of reducing costs and improving productivity by migrating and consolidating existing application software onto state-of-the-art computer hardware. Integral to this effort is: the Government's attempt to optimize the hardware data storage configurations required to support its users. Through simulation modeling, the BMC manager can analyze alternative configurations without actually incurring the associated expense. The simulation effort discussed in this paper describes an approach taken to model the DASD subsystem. A model was built using the SLAM simulation language.