Managing RAID on Linux(1).pdf

RAID

LINUX

Derek Vadala

Beijing • Cambridge • Farnham • Köln • Paris • Sebastopol • Taipei • Tokyo

Managing

Managing RAID on Linux

by Derek Vadala

Printed in the United States of America.

Published by O’Reilly & Associates, Inc., 1005 Gravenstein Highway North, Sebastopol, CA

95472.

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Editor:

Andy Oram

Production Editor:

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Cover Designer:

Emma Colby

Interior Designer:

David Futato

Printing History:

December 2002: First Edition.

Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered

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in this book, and O’Reilly & Associates, Inc. was aware of a trademark claim, the designations

have been printed in caps or initial caps. The association between the image of a logjam and the

topic of RAID on Linux is a trademark of O’Reilly & Associates, Inc.

While every precaution has been taken in the preparation of this book, the publisher and author

assume no responsibility for errors or omissions, or for damages resulting from the use of the

information contained herein.

ISBN: 1-56592-730-3

[M]

Table of Contents

Preface

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

vii

1. Introduction

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

RAID Terminology

The RAID Levels: An Overview

RAID on Linux

Hardware Versus Software

2. Planning and Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hardware or Software?

The RAID Levels: In Depth

RAID Case Studies: What Should I Choose?

Disk Failures

Hardware Considerations

Making Sense of It All

3. Getting Started: Building a Software RAID

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Kernel Configuration

Working with Software RAID

Creating an Array

The Next Step

105

4. Software RAID Reference

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

106

Kernel Options

106

md Block Special Files

109

/proc and Software RAID

109

raidtools

114

mdadm

129

5. Hardware RAID

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

145

Choosing a RAID Controller

145

Preparing Controllers and Disks

148

General Configuration Issues

150

Mylex

155

Adaptec

167

Promise Technology

174

3ware Escalade ATA RAID Controller

181

LSI Logic (MegaRAID)

184

6. Filesystems

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

187

Basic Filesystem Concepts

188

The Linux Virtual Filesystem (VFS)

191

ext2

192

ext3 Extensions for the ext2 Filesystem

197

ReiserFS

201

IBM JFS

207

SGI XFS

210

7. Performance, Tuning, and Maintenance

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

214

Monitoring RAID Devices

214

Managing Disk Failures

216

Configuring Hard Disk Parameters

221

Performance Testing

227

Booting with Software RAID

227

A. Additional Resources

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

233

B. Hardware RAID Controller Vendors

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

236

Index

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

237

Table of Contents

Preface

Linux has come a long way in the last decade. No longer relegated to the world of

hobbyists and developers, Linux is ubiquitous and is quickly taking hold of enter-

prise and high-performance computing. Established corporations such as IBM,

Hewlett-Packard, and Sun Microsystems have embraced Linux. Linux is now used to

produce blockbuster motion pictures, create real-time models of worldwide weather

patterns, and aid in scientific and medical research. Linux is even used on the Inter-

national Space Station.

Linux has accomplished this because of a vast, and seemingly tireless, network of

developers, documenters, and evangelists who share the common mantra that soft-

ware should be reliable, efficient, and secure as well as free. The hard work of these

individuals has propelled Linux into the mainstream. Their focus on technologies

that allow Linux to compete with traditional operating systems certainly accounts for

a large part of the success of Linux.

This book focuses on using one of those technologies: RAID, also known as a

Redundant Array of Inexpensive Disks. As you will find out, RAID allows individu-

als and organizations to get more out of their hardware by increasing the perfor-

mance and reliability of their data. RAID is but one component of what makes Linux

a competitive platform.

Overview of the Book

Here is a brief overview of the contents of this book.

Chapter 1, Introduction , provides a quick overview of RAID on Linux, including its

evolution and future direction. The chapter briefly outlines the RAID levels and iden-

tifies which are available under Linux through hardware or software.

Chapter 2, Planning and Architecture , helps you determine what type of RAID is best

suited for your needs. The chapter focuses on the differences between hardware and

software RAIDs and discusses which is the best choice, depending on your budget

vii

This is the Title of the Book, eMatter Edition

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