From Open VMS Operating System Concepts, Second Edition

Overview

Before learning about files and file structures, it is necessary to understand the physical structure of the common secondary [1] storage medium, the magnetic disk. In large measure, the disk's physical structure and its limitations dictate how it is used to store data files. To be specific, a disk is the magnetic medium on which the data are stored. A disk drive is a larger hardware system that includes the disk and its supporting machinery record-playback (or read-write) heads, the arm that holds them, the positioner (or actuator) that moves them, the motor that spins the disk, and the electronics that control these components. To this end, the characteristics of disks and disk drives are presented first.

After describing the hardware, we will turn to the logical organization of the data on the disk. The logical file structure is maintained by the file subsystem, a subset of the operating system. No general purpose operating system is functional unless it has file system capabilities, no matter how primitive. The only exception to this observation is an embedded real-time operating system in which the entire application, its data, and the operating system are permanently memory-resident, for instance, a weapons control system on a tactical fighter plane or the software in an automobile. Typical of these real-time systems are RSX-11S for the PDP-11 and some operating systems for microcomputers, like the 68000 family.

[1]The primary storage medium is memory. Tape is normally considered a tertiary

Copyright Butterworth-Heinemann 1997 under license agreement with Books24x7

Products & Services
Backup and Recovery Software
Backup software and recovery software creates copies of files, databases, disks, drives, or entire computer systems to avoid the permanent loss of data. These applications also enable the retrieval of data from damaged files, storage devices, or file systems.
Data Security Software
Data security software restricts access to stored data and processes on a computer or server. These applications are designed to prevent data loss, corruption, or disclosure of sensitive information.
Data Recovery Services
Data recovery services enable the retrieval of inaccessible or contaminated data from a secondary storage media that has been damaged.
Computers
Computers are programmable electronic devices that accept data, execute prerecorded instructions, perform mathematical and logical operations, and output results.
Data Storage Systems
Data storage systems are used to store, protect and manage computer data. Many types of disk drives and tape drives are available.

Topics of Interest

Overview Most operating systems texts present a chapter on the broad history of operating systems. We deviate from this practice by looking at this history as it took shape in a single company,...

OVERVIEW The configuration of a Digital UNIX system is a broad topic that touches every possible system and user subsystem and service, both hardware and software. Rather than attempt to cover each...

Exam 70-290: Objective 1 Introduction Disk management is an important aspect of optimizing and maintaining any PC, and Windows Server 2003 includes a variety of tools that the administrator can use...

Introduction Disk management is an important aspect of optimizing and maintaining any server and Windows Server 2003 includes a variety of tools that the administrator can use to format, partition,...

Introduction Most computers have multiple file systems such as physical drives, network drives, and removable drives that you as the administrator need to manage. By the end of this chapter, you will...