Red Hat ENTERPRISE LINUX 4 - DEVELOPER TOOLS GUIDE Manual

Red Hat Enterprise Linux 4
Global Network
Block Device
Using GNBD with Red Hat Global File System

Global Network Block Device
Red Hat Enterprise Linux 4 Global Network Block Device
Using GNBD with Red Hat Global File System
Edition 1.0
Copyright © 2009 Red Hat, Inc. This material may only be distributed subject to the terms and
conditions set forth in the Open Publication License, V1.0 or later (the latest version of the OPL is
presently available at http://www.opencontent.org/openpub/).
Red Hat and the Red Hat "Shadow Man" logo are registered trademarks of Red Hat, Inc. in the United
States and other countries.
All other trademarks referenced herein are the property of their respective owners.
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This book provides an overview on using Global Network Block Device (GNBD) with Red Hat GFS for
Red Hat Enterprise Linux 4.

iii
Introduction v
1. About This Guide ............................................................................................................ v
2. Audience ........................................................................................................................ v
3. Software Versions ........................................................................................................... v
4. Related Documentation ................................................................................................... v
5. Document Conventions ................................................................................................... vi
5.1. Typographic Conventions ..................................................................................... vi
5.2. Pull-quote Conventions ....................................................................................... viii
5.3. Notes and Warnings ........................................................................................... viii
6. Feedback ....................................................................................................................... ix
1. Using GNBD with Red Hat GFS 1
2. Considerations for Using GNBD with Device-Mapper Multipath 3
2.1. Linux Page Caching ..................................................................................................... 3
2.2. Fencing GNBD Server Nodes ....................................................................................... 3
3. GNBD Driver and Command Usage 5
3.1. Exporting a GNBD from a Server .................................................................................. 5
3.2. Importing a GNBD on a Client ...................................................................................... 7
4. Running GFS on a GNBD Server Node 9
A. Revision History 11
Index 13

iv

v
Introduction
1. About This Guide
This book describes how to use Global Network Block Device (GNDB) with Global File System (GFS),
including information about device-mapper multipath, GNDB driver and command usage, and running
GFS on a GNBD server node.
2. Audience
This book is intended to be used by system administrators managing systems running the Linux
operating system. It requires familiarity with Red Hat Enterprise Linux and GFS file system
administration.
3. Software Versions
Software Description
RHEL4 refers to RHEL4 and higher
GFS refers to GFS 6.1 and higher
Table 1. Software Versions
4. Related Documentation
For more information about using Red Hat Enterprise Linux, refer to the following resources:
•Red Hat Enterprise Linux Installation Guide — Provides information regarding installation of Red
Hat Enterprise Linux.
•Red Hat Enterprise Linux Introduction to System Administration — Provides introductory information
for new Red Hat Enterprise Linux system administrators.
•Red Hat Enterprise Linux System Administration Guide — Provides more detailed information about
configuring Red Hat Enterprise Linux to suit your particular needs as a user.
•Red Hat Enterprise Linux Reference Guide — Provides detailed information suited for more
experienced users to reference when needed, as opposed to step-by-step instructions.
•Red Hat Enterprise Linux Security Guide — Details the planning and the tools involved in creating a
secured computing environment for the data center, workplace, and home.
For more information about Red Hat Cluster Suite for Red Hat Enterprise Linux, refer to the following
resources:
•Red Hat Cluster Suite Overview — Provides a high level overview of the Red Hat Cluster Suite.
•Configuring and Managing a Red Hat Cluster — Provides information about installing, configuring
and managing Red Hat Cluster components.
•Global File System: Configuration and Administration — Provides information about installing,
configuring, and maintaining Red Hat GFS (Red Hat Global File System).

Introduction
vi
•LVM Administrator's Guide: Configuration and Administration — Provides a description of the
Logical Volume Manager (LVM), including information on running LVM in a clustered environment.
•Using Device-Mapper Multipath — Provides information about using the Device-Mapper Multipath
feature of Red Hat Enterprise Linux.
•Linux Virtual Server Administration — Provides information on configuring high-performance
systems and services with the Linux Virtual Server (LVS).
•Red Hat Cluster Suite Release Notes — Provides information about the current release of Red Hat
Cluster Suite.
Red Hat Cluster Suite documentation and other Red Hat documents are available in HTML and PDF
versions online at the following location:
http://www.redhat.com/docs
5. Document Conventions
This manual uses several conventions to highlight certain words and phrases and draw attention to
specific pieces of information.
In PDF and paper editions, this manual uses typefaces drawn from the Liberation Fonts1 set. The
Liberation Fonts set is also used in HTML editions if the set is installed on your system. If not,
alternative but equivalent typefaces are displayed. Note: Red Hat Enterprise Linux 5 and later includes
the Liberation Fonts set by default.
5.1. Typographic Conventions
Four typographic conventions are used to call attention to specific words and phrases. These
conventions, and the circumstances they apply to, are as follows.
Mono-spaced Bold
Used to highlight system input, including shell commands, file names and paths. Also used to highlight
key caps and key-combinations. For example:
To see the contents of the file my_next_bestselling_novel in your current
working directory, enter the cat my_next_bestselling_novel command at the
shell prompt and press Enter to execute the command.
The above includes a file name, a shell command and a key cap, all presented in Mono-spaced Bold
and all distinguishable thanks to context.
Key-combinations can be distinguished from key caps by the hyphen connecting each part of a key-
combination. For example:
Press Enter to execute the command.
Press Ctrl+Alt+F1 to switch to the first virtual terminal. Press Ctrl+Alt+F7 to
return to your X-Windows session.
The first sentence highlights the particular key cap to press. The second highlights two sets of three
key caps, each set pressed simultaneously.
1 https://fedorahosted.org/liberation-fonts/

Typographic Conventions
vii
If source code is discussed, class names, methods, functions, variable names and returned values
mentioned within a paragraph will be presented as above, in Mono-spaced Bold. For example:
File-related classes include filesystem for file systems, file for files, and dir for
directories. Each class has its own associated set of permissions.
Proportional Bold
This denotes words or phrases encountered on a system, including application names; dialogue
box text; labelled buttons; check-box and radio button labels; menu titles and sub-menu titles. For
example:
Choose System > Preferences > Mouse from the main menu bar to launch Mouse
Preferences. In the Buttons tab, click the Left-handed mouse check box and click
Close to switch the primary mouse button from the left to the right (making the mouse
suitable for use in the left hand).
To insert a special character into a gedit file, choose Applications > Accessories
> Character Map from the main menu bar. Next, choose Search > Find… from the
Character Map menu bar, type the name of the character in the Search field and
click Next. The character you sought will be highlighted in the Character Table.
Double-click this highlighted character to place it in the Text to copy field and then
click the Copy button. Now switch back to your document and choose Edit > Paste
from the gedit menu bar.
The above text includes application names; system-wide menu names and items; application-specific
menu names; and buttons and text found within a GUI interface, all presented in Proportional Bold and
all distinguishable by context.
Note the > shorthand used to indicate traversal through a menu and its sub-menus. This is to avoid
the difficult-to-follow 'Select Mouse from the Preferences sub-menu in the System menu of the main
menu bar' approach.
Mono-spaced Bold Italic or Proportional Bold Italic
Whether Mono-spaced Bold or Proportional Bold, the addition of Italics indicates replaceable or
variable text. Italics denotes text you do not input literally or displayed text that changes depending on
circumstance. For example:
To connect to a remote machine using ssh, type ssh [e-mail] at
a shell prompt. If the remote machine is example.com and your username on that
machine is john, type ssh [email protected].
The mount -o remount file-system command remounts the named file
system. For example, to remount the /home file system, the command is mount -o
remount /home.
To see the version of a currently installed package, use the rpm -q package
command. It will return a result as follows: package-version-release.
Note the words in bold italics above — username, domain.name, file-system, package, version and
release. Each word is a placeholder, either for text you enter when issuing a command or for text
displayed by the system.

Introduction
viii
Aside from standard usage for presenting the title of a work, italics denotes the first use of a new and
important term. For example:
When the Apache HTTP Server accepts requests, it dispatches child processes
or threads to handle them. This group of child processes or threads is known as
a server-pool. Under Apache HTTP Server 2.0, the responsibility for creating and
maintaining these server-pools has been abstracted to a group of modules called
Multi-Processing Modules (MPMs). Unlike other modules, only one module from the
MPM group can be loaded by the Apache HTTP Server.
5.2. Pull-quote Conventions
Two, commonly multi-line, data types are set off visually from the surrounding text.
Output sent to a terminal is set in Mono-spaced Roman and presented thus:
books Desktop documentation drafts mss photos stuff svn
books_tests Desktop1 downloads images notes scripts svgs
Source-code listings are also set in Mono-spaced Roman but are presented and highlighted as
follows:
package org.jboss.book.jca.ex1;
import javax.naming.InitialContext;
public class ExClient
{
public static void main(String args[])
throws Exception
{
InitialContext iniCtx = new InitialContext();
Object ref = iniCtx.lookup("EchoBean");
EchoHome home = (EchoHome) ref;
Echo echo = home.create();
System.out.println("Created Echo");
System.out.println("Echo.echo('Hello') = " + echo.echo("Hello"));
}
}
5.3. Notes and Warnings
Finally, we use three visual styles to draw attention to information that might otherwise be overlooked.

Feedback
ix
Note
A note is a tip or shortcut or alternative approach to the task at hand. Ignoring a note
should have no negative consequences, but you might miss out on a trick that makes your
life easier.
Important
Important boxes detail things that are easily missed: configuration changes that only
apply to the current session, or services that need restarting before an update will apply.
Ignoring Important boxes won't cause data loss but may cause irritation and frustration.
Warning
A Warning should not be ignored. Ignoring warnings will most likely cause data loss.
6. Feedback
If you spot a typo, or if you have thought of a way to make this manual better, we would love to
hear from you. Please submit a report in Bugzilla (http://bugzilla.redhat.com/bugzilla/) against the
component rh-cs.
Be sure to mention the manual's identifier:
rh-gfs(EN)-4.8 (2009-05-15T15:10)
By mentioning this manual's identifier, we know exactly which version of the guide you have.
If you have a suggestion for improving the documentation, try to be as specific as possible. If you have
found an error, please include the section number and some of the surrounding text so we can find it
easily.

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