The DRBD User's Guide
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The DRBD User's Guide

Florian Haas

Philipp Reisner

Lars Ellenberg

This guide has been released to the DRBD community, and its authors strive to improve it permanently. Feedback from readers is always welcome and encouraged. Please use the DRBD public mailing list for enhancement suggestions and corrections. Recent content additions are marked with Draft status; feedback on those sections is particularly highly appreciated.

Copyright © 2008 LINBIT Information Technologies GmbH

Trademarks used in this book

DRBD, the DRBD logo, LINBIT, and the LINBIT logo are trademarks or registered trademarks of LINBIT Information Technologies GmbH in Austria, the United States and other countries.

AMD is a registered trademark of Advanced Micro Devices, Inc.

Debian is a registered trademark of Software in the Public Interest, Inc.

IBM is a registered trademark of International Business Machines Corporation.

Intel is a registered trademark of Intel Corporation.

Linux is a registered trademark of Linus Torvalds.

MySQL and MySQL Enterprise are trademarks or registered trademarks of MySQL AB and/or Sun Microsystems, Inc.

Oracle is a registered trademark of Oracle Corporation and/or its affiliates.

Red Hat, Red Hat Enterprise Linux, and RPM are trademarks or registered trademarks of Red Hat, Inc.

SuSE, SUSE, and SUSE Linux Enterprise Server are trademarks or registered trademarks of Novell, Inc.

Xen is a registered trademark of XenSource, Inc.

Other names mentioned in this book may be trademarks or registered trademarks of their respective owners.

Table of Contents

About this guide

I. Introduction to DRBD

1. DRBD Fundamentals

Kernel module
User space administration tools
Resources
Resource roles

2. DRBD Features

Single-primary mode
Dual-primary mode
Replication modes
Efficient synchronization
On-line device verification
Replication traffic integrity checking
Automatic split brain recovery
Support for disk flushes
Disk error handling strategies
Strategies for dealing with outdated data

II. Building, installing and configuring DRBD

3. Installing pre-built DRBD binary packages

Packages supplied by LINBIT
Packages supplied by distribution vendors

4. Building and installing DRBD from source

Downloading the DRBD sources

Building DRBD from source

Checking build prerequisites
Preparing the kernel source tree
Compiling DRBD as a kernel module
Patching DRBD into the kernel

Installing DRBD

Building a DRBD RPM package

Building a DRBD Debian package

5. Configuring DRBD

Preparing your lower-level storage

Preparing your network configuration

Configuring your resource

Example configuration
The global section
The common section
The resource sections

Enabling your resource for the first time

The initial device synchronization

III. Working with DRBD

6. Common administrative tasks

Checking DRBD status

Status information in /proc/drbd
Connection states
Resource roles
Disk states

Enabling and disabling resources

Enabling resources
Disabling resources

Reconfiguring resources

Promoting and demoting resources

Enabling dual-primary mode

Using on-line device verification

Enabling on-line verification
Invoking on-line verification
Automating on-line verification

Configuring the rate of synchronization

Permanent syncer rate configuration
Temporary syncer rate configuration

Configuring I/O error handling strategies

Resizing resources

Growing on-line
Growing off-line
Shrinking on-line
Shrinking off-line

Disabling backing device flushes

7. Troubleshooting and error recovery

Dealing with hard drive failure

Manually detaching DRBD from your hard drive
Automatic detach on I/O error
Replacing a failed disk when using internal meta data
Replacing a failed disk when using external meta data

Dealing with node failure

Dealing with temporary secondary node failure
Dealing with temporary primary node failure
Dealing with permanent node failure

Dealing with split brain

IV. DRBD-enabled applications

8. Integrating DRBD with Heartbeat clusters

Heartbeat primer

The Heartbeat cluster manager
Heartbeat resources
Heartbeat resource agents
Heartbeat communication channels

Heartbeat configuration

The ha.cf file
The authkeys file
Propagating the cluster configuration to cluster nodes

Using DRBD in Heartbeat R1-style clusters

Heartbeat R1-style configuration
Managing Heartbeat R1-style clusters

Using DRBD in Heartbeat CRM-enabled clusters

Heartbeat CRM configuration
Managing Heartbeat CRM clusters

Using Heartbeat with dopd

Heartbeat configuration
DRBD Configuration
Testing dopd functionality

9. Using LVM with DRBD

LVM primer
Using a Logical Volume as a DRBD backing device
Configuring a DRBD resource as a Physical Volume
Nested LVM configuration with DRBD

10. Using GFS with DRBD

Creating a DRBD resource suitable for GFS

Configuring LVM to recognize the DRBD resource

Configuring your cluster to support GFS

Red Hat Enterprise Linux 4

Creating a GFS filesystem

Using your GFS filesystem

11. Using Xen with DRBD

Xen primer
Creating a DRBD resource suitable to act as a Xen VBD
Using DRBD VBDs
Starting, stopping, and migrating DRBD-backed domU's
Internals of DRBD/Xen integration
Integrating Xen with Heartbeat

V. Learning more about DRBD

12. DRBD Internals

DRBD meta data

Internal meta data
External meta data
Estimating meta data size

Generation Identifiers

Data generations
The generation identifier tuple
How generation identifiers change
How DRBD uses generation identifiers

The Activity Log

Purpose
Active extents
Selecting a suitable Activity Log size

The quick-sync bitmap

The peer outdater interface

13. Getting more information

Public mailing list
Commercial DRBD support
Publications
Other useful resources

A. DRBD system manual pages

drbd.conf — Configuration file for DRBD's devices
drbdadm — Administration tool for DRBD
drbdsetup — Setup tool for DRBD
drbdmeta — DRBD's meta data management tool

List of Figures

1.1. DRBD's position within the Linux I/O stack
9.1. LVM overview
12.1. GI tuple changes at start of a new data generation
12.2. GI tuple changes at start of re-synchronization
12.3. GI tuple changes at completion of re-synchronization

List of Tables

12.1. Peer outdater exit codes

List of Examples

A.1. A small drbd.conf file

List of Equations

2.1. Synchronization time
6.1. Syncer rate example, 110MB/s effective available bandwidth
6.2. Syncer rate example, 80MB/s effective available bandwidth
12.1. Calculating DRBD meta data size (exactly)
12.2. Estimating DRBD meta data size (approximately)
12.3. Active extents calculation based on sync rate and target sync time
12.4. Active extents calculation based on sync rate and target sync time (example)

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