Support Policies for RHEL High Availability Clusters - corosync-qdevice and corosync-qnetd

Updated -

Contents

Overview

Applicable Environments

  • Red Hat Enterprise Linux (RHEL) with the High Availability Add-On
  • Cluster architectures involving a quorum device provided through qdevice and qnetd

Useful References and Guides

Introduction

This policy guide explains Red Hat's requirements and support limitations regarding quorum devices using corosync-device and corosync-qnetd in a RHEL High Availability cluster.

Policies

Available/Supported Releases:

  • RHEL 8 & 9: corosync-qdevice and corosync-qnetd are supported by Red Hat
  • RHEL 7: corosync-qdevice and corosync-qnetd are supported technologies as of RHEL 7.4 - using releases corosync-qdevice-2.4.0-9.el7 and corosync-qnetd-2.4.0-9.el7 or later.
    • NOTE: qdevice and qnetd are available for usage in RHEL High Availability clusters starting with RHEL 7 Update 3, but are considered a Technology Preview in that release.
  • Mix of RHEL 7 qdevice and RHEL 8 qnetd or vice versa RHEL 8 qdevice and RHEL 7 qnetd: supported.
    • EXAMPLE: Our cluster is based on RHEL 8 but we would like to use our RHEL 7 arbiter (qnetd). This is possible and supported.
    • EXAMPLE: Our cluster is based on RHEL 7 but we would like to introduce an arbiter (qnetd) on RHEL 8. This is possible and supported.

Mixing Bare Metal and Virtual Platforms

  • It is possible and supported to use a virtual machine qnetd server with a cluster made up of bare metal members or members on a different virtualization platform.
  • It is possible and supported to use a bare metal qnetd server with a cluster made up of virtual machine members.
  • All support policies related to the cluster members' platforms still apply.

Number of Quorum Devices / Servers: A cluster may only utilize a single qdevice interacting with a single qnetd quorum server.

Number of Clusters per Quorum Device / Server: Multiple clusters may utilize the same qnetd quorum server.

Quorum device heuristics: corosync-qdevice provides functionality that allows an administrator to configure "heuristics" that evaluate true or false and influence the scoring algorithm of qdevice. This functionality is subject to the following conditions:

  • RHEL 8: Heuristics functionality is provided as a Technology Preview.
  • RHEL 7: Heuristics functionality is provided as a Technology Preview in RHEL 7.7 and 7.6. This functionality was not available in earlier releases of RHEL 7.

Additional information

The quorum device (package corosync-qnetd) should never be installed in one of the cluster nodes, it has to be hosted in a system aside. Hosting it in one of the cluster nodes is not supported.

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