Chapter 2. Planning your Instance HA deployment

Before you deploy Instance HA, review the following considerations:

  • Compute node host names and Pacemaker remote resource names must comply with the W3C naming conventions. For more information, see Declaring Namespaces and Names and Tokens in the W3C documentation.
  • Typically, Instance HA requires that you configure shared storage for disk images of instances. Therefore, if you attempt to use the no-shared-storage option, you might receive an InvalidSharedStorage error during evacuation, and the instances will not start on another Compute node.

    However, if all your instances are configured to boot from an OpenStack Block Storage (cinder) volume, you do not need to configure shared storage for the disk image of the instances, and you can evacuate all instances using the no-shared-storage option.

    During evacuation, if your instances are configured to boot from a Block Storage volume, any evacuated instances boot from the same volume on another Compute node. Therefore, the evacuated instances immediately restart their jobs because the OS image and the application data are stored on the OpenStack Block Storage volume.

  • If you deploy Instance HA in a Spine-Leaf environment, you must define a single internal_api network for the Controller and Compute nodes. You can then define a subnet for each leaf. For more information about configuring Spine-Leaf networks, see Creating a roles data file in the Spine Leaf Networking guide.
  • From Red Hat OpenStack Platform 13 and later, you use director to upgrade Instance HA as a part of the overcloud upgrade. For more information about upgrading the overcloud, see Keeping Red Hat OpenStack Platform Updated guide.
  • Disabling Instance HA with the director after installation is not supported. For a workaround to manually remove Instance HA components from your deployment, see the article How can I remove Instance HA components from the controller nodes? .

    Important

    This workaround is not verified for production environments. You must verify the procedure in a test environment before you implement it in a production environment.