CHAPTER 10

Mass-Storage Structure

The file system can be viewed logically as consisting of three parts. In Chapter 11, we examine the user and programmer interface to the file system. In Chapter 12, we describe the internal data structures and algorithms used by the operating system to implement this interface. In this chapter, we begin a discussion of file systems at the lowest level: the structure of secondary storage. 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 maximize performance. Next, we discuss disk formatting and management of boot blocks, damaged blocks, and swap space. We conclude with an examination of the structure of RAID systems.

CHAPTER OBJECTIVES

  • To describe the physical structure of secondary storage devices and its effects on the uses of the devices.
  • To explain the performance characteristics of mass-storage devices.
  • To evaluate disk scheduling algorithms.
  • To discuss operating-system services provided for mass storage, including RAID

10.1 Overview of Mass-Storage Structure

In this section, we present a general overview of the physical structure of secondary and tertiary storage devices.

10.1.1 Magnetic Disks

Magnetic disks provide the bulk of secondary storage for modern computer systems. Conceptually, disks are relatively simple (Figure 10.1). Each disk platter has a flat circular shape, like a CD. Common platter diameters range from 1.8 ...

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