This guide describes DRBD version 8.4 and above. For 8.3 please look here.


Chapter 9. Integrating DRBD with Red Hat Cluster

Table of Contents

9.1. Red Hat Cluster background information
9.1.1. Fencing
9.1.2. The Resource Group Manager
9.2. Red Hat Cluster configuration
9.2.1. The cluster.conf file
9.3. Using DRBD in Red Hat Cluster fail-over clusters
9.3.1. Setting up your cluster configuration

This chapter describes using DRBD as replicated storage for Red Hat Cluster high availability clusters.

[Note]Note

This guide uses the unofficial term Red Hat Cluster to refer to a product that has had multiple official product names over its history, including Red Hat Cluster Suite and Red Hat Enterprise Linux High Availability Add-On.

9.1. Red Hat Cluster background information

9.1.1. Fencing

Red Hat Cluster, originally designed primarily for shared storage clusters, relies on node fencing to prevent concurrent, uncoordinated access to shared resources. The Red Hat Cluster fencing infrastructure relies on the fencing daemon fenced, and fencing agents implemented as shell scripts.

Even though DRBD-based clusters utilize no shared storage resources and thus fencing is not strictly required from DRBD’s standpoint, Red Hat Cluster Suite still requires fencing even in DRBD-based configurations.

9.1.2. The Resource Group Manager

The resource group manager ( rgmanager, alternatively clurgmgr) is akin to Pacemaker. It serves as the cluster management suite’s primary interface with the applications it is configured to manage.

9.1.2.1. Red Hat Cluster resources

A single highly available application, filesystem, IP address and the like is referred to as a resource in Red Hat Cluster terminology.

Where resources depend on each other — such as, for example, an NFS export depending on a filesystem being mounted — they form a resource tree, a form of nesting resources inside another. Resources in inner levels of nesting may inherit parameters from resources in outer nesting levels. The concept of resource trees is absent in Pacemaker.

9.1.2.2. Red Hat Cluster services

Where resources form a co-dependent collection, that collection is called a service. This is different from Pacemaker, where such a collection is referred to as a resource group.

9.1.2.3. rgmanager resource agents

The resource agents invoked by rgmanager are similar to those used by Pacemaker, in the sense that they utilize the same shell-based API as defined in the Open Cluster Framework (OCF), although Pacemaker utilizes some extensions not defined in the framework. Thus in theory, the resource agents are largely interchangeable between Red Hat Cluster Suite and Pacemaker — in practice however, the two cluster management suites use different resource agents even for similar or identical tasks.

Red Hat Cluster resource agents install into the /usr/share/cluster directory. Unlike Pacemaker OCF resource agents which are by convention self-contained, some Red Hat Cluster resource agents are split into a .sh file containing the actual shell code, and a .metadata file containing XML resource agent metadata.

DRBD includes a Red Hat Cluster resource agent. It installs into the customary directory as drbd.sh and drbd.metadata.


This guide describes DRBD version 8.4 and above. For 8.3 please look here.