Administrative Procedures for RHEL High Availability Clusters - Enabling sbd fencing in RHEL 6

Updated

Contents

Overview

Applicable Environments

  • Red Hat Enterprise Linux (RHEL) 6 with the High Availability Add-On

Useful References and Guides

Introduction

This article focuses on deploying sbd fencing in a RHEL 6 High Availability cluster.

Red Hat's series of Administrative Procedures for RHEL High Availability Clusters aims to deliver simple and direct instruction for configuring common use cases using typical or recommended settings. There may be additional features, options, and decisions relevant to the targeted components that organizations may wish to consider for their deployments, whereas this guide can serve as a helpful reference for understanding how to get up and running with typical settings quickly. The above references and guides may be a useful starting point to understand these components and the High Availability technologies in more detail.

Prepare the environment

Prerequisites for enabling sbd fencing

  • RHEL 6 server cluster members have operating system and cluster software installed
  • Cluster has been setup (e.g., pcs cluster setup)
  • Cluster has an odd-number of members

Install software

On every node:

# yum install sbd

Confirm a suitable watchdog device

Each node must have access to a watchdog timer device that meets Red Hat's support requirements and that will perform the necessary reset functions. This is a good time to stop and confirm that each node's watchdog timer device meets those requirements and performs as expected in testing.

Enable and configure sbd health and quorum monitoring

Configure the cluster to run sbd

NOTE: This will restart the cluster entirely to enable sbd on all nodes. Only proceed if the cluster is in a state where nodes and resources are able to undergo an outage.

Enable sbd health and quorum monitoring with:

# # Syntax: # pcs stonith sbd enable [--watchdog=<path>[@<node>]] ... [<SBD_OPTION>=<value>]
# # Example:
# pcs stonith sbd enable

See pcs stonith help and Red Hat's design guidance on sbd for further guidance on enabling sbd with various options that are available.

Configure cluster fence method

Enable stonith-watchdog-timeout fencing

Configure the cluster with a greater than 0 value for the cluster property stonith-watchdog-timeout. This value should be larger than the SBD_WATCHDOG_TIMEOUT setting configured in the earlier pcs stonith sbd enable step - which defaults to a value of 5 seconds. If SBD_WATCHDOG_TIMEOUT was left at the default, this stonith-watchdog-timeout property can be set to 10s. 

# # Example with SBD_WATCHDOG_TIMEOUT=5 (seconds)
# pcs property set stonith-watchdog-timeout 10s

For more information on choosing this value, see Red Hat's design guidance for sbd fencing:

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