Operating System Concepts Essentials

Chapter 11. Mass-Storage Structure

The file system can be viewed logically as consisting of three parts. In Chapter 9, we examined the user and programmer interface to the file system. In Chapter 10, we described the internal data structures and algorithms used by the operating system to implement this interface. In this chapter, we discuss the lowest level of the file system: the mass storage structures. We first describe the physical structure of magnetic disks and magnetic tapes. We then describe disk-scheduling algorithms, which schedule the order of disk I/Os to improve performance. Next, we discuss disk formatting and management of boot blocks, damaged blocks, and swap space. We then examine mass storage structure, covering disk reliability. We conclude with coverage of RAID architecture.

CHAPTER OBJECTIVES

• To describe the physical structure of mass-storage devices and its effects on the uses of the devices.

• To explain the performance characteristics of mass-storage devices.

• To discuss operating-system services provided for mass storage, including RAID and HSM.

Overview of Mass-Storage Structure

In this section, we present a general overview of the physical structure of mass-storage devices.

Magnetic Disks

Magnetic disks provide the bulk of mass storage for modern computer systems. Conceptually, disks are relatively simple (Figure 11.1). Each disk platter has a flat circular shape, like a CD. Common platter diameters range from1.8 to 5.25 inches. The two surfaces of a platter are ...