Appendix A. Deployment migration options

This section includes topics related to migrating to a distributed compute node architecture and multi-stack deployments.

A.1. Migrating to a spine and leaf deployment

It is possible to migrate an existing cloud with a pre-existing network configuration to one with a spine leaf architecture. For this, the following conditions are needed:

  • All bare metal ports must have their physical-network property value set to ctlplane.
  • The parameter enable_routed_networks is added and set to true in undercloud.conf, followed by a re-run of the undercloud installation command, openstack undercloud install.

Once the undercloud is re-deployed, the overcloud is considered a spine leaf, with a single leaf leaf0. You can add additional provisioning leaves to the deployment through the following steps.

  1. Add the desired subnets to undercloud.conf as shown in Configuring routed spine-leaf in the undercloud.
  2. Re-run the undercloud installation command, openstack undercloud install.
  3. Add the desired additional networks and roles to the overcloud templates, network_data.yaml and roles_data.yaml respectively.

    Note

    If you are using the {{network.name}}InterfaceRoutes parameter in the network configuration file, then you’ll need to ensure that the NetworkDeploymentActions parameter includes the value UPDATE.

      NetworkDeploymentActions: ['CREATE','UPDATE'])
  4. Finally, re-run the overcloud installation script that includes all relevant heat templates for your cloud deployment.

A.2. Migrating to a multistack deployment

You can migrate from a single stack deployment to a multistack deployment by treating the existing deployment as the central site, and adding additional edge sites.

The ability to migrate from single to multistack in this release is a Technology Preview, and therefore is not fully supported by Red Hat. It should only be used for testing, and should not be deployed in a production environment. For more information about Technology Preview features, see Scope of Coverage Details.

You cannot split the existing stack. You can scale down the existing stack to remove compute nodes if needed. These compute nodes can then be added to edge sites.

Note

This action creates workload interruptions if all compute nodes are removed.