Chapter 16 - Overview of Disks

Abstract

Disk technology has advanced tremendously in the past few years. This chapter provides the background knowledge to study some of the design issues and trade-offs that can affect the performance of a disk drive and disk-based storage subsystems. Emphasis in performance discussion is the major attribute. Since the beginning, and continuing to today, four major forces drive the continual developments and evolutions in disk drive technologies—namely, capacity, cost, performance, and reliability. Computer users are always hungry for more storage space. There are two supporting software constituents that reside in the host system: the file system and the disk driver. Unlike the DRAM main memory, which a user's program makes direct access to, an operating system typically provides the service for storing and retrieving data to and from a disk-based storage on behalf of the application program. The file system and the disk driver are the two operating system components providing this service. The demise of the disk drive as the most cost-effective way of providing cheap secondary storage at an acceptable level of performance has every now and then been predicted by some over the years. Disk drives will also find more and more applications outside of the computing world.