Hardware and Its Parameters

This chapter summarizes the hardware used to store data files: mainly tapes and disks. These descriptions will provide background for the understanding of their operation and performance; in other words, the concern here is what the devices do rather than how they do it. After this chapter all analysis refering to hardware will be made using a limited number of parameters and concepts established here. Six parameters are adequate to describe the performance of all types of current hardware with sufficient precision. The material is organized into two major interrelated sections: the first section contains a review of the types of hardware available, and the second section discusses the parameters used to describe hardware. Along with basic performance data, cost estimates are provided since the benefits of good performance cannot be separated from the expenses associated with powerful devices. Section 2-3 presents hardwarerelated programming concepts, and the chapter concludes with a summary of the parameters for recall and reference. Chapter 13 provides some further discussion of storage system architecture. The remainder of the book needs to make very few direct references to hardware