Chapter 1. Creating a deployment with separate heat stacks When you use separate heat stacks in your Red Hat OpenStack Platform environment, you can isolate the management operations that director performs. For example, you can scale Compute nodes without updating the Controller nodes that the control plane stack manages. You can also use this technique to deploy multiple Red Hat Ceph Storage clusters. 1.1. Using separate heat stacks In a typical Red Hat OpenStack Platform deployment, a single heat stack manages all nodes, including the control plane (Controllers). You can now use separate heat stacks to address architectural constraints. Use separate heat stacks for different node types. For example, the control plane, Compute nodes, and HCI nodes can each be managed by their own stack. This allows you to change or scale the compute stack without affecting the control plane. You can use separate heat stacks at the same site to deploy multiple Ceph clusters. You can use separate heat stacks for disparate availability zones (AZs) within the same data center. Separate heat stacks are required for deploying Red Hat OpenStack Platform using a distributed compute node (DCN) architecture. This reduces network and management dependencies on the central data center. Each edge site in this architecture must also have its own AZ from both Compute and Storage nodes. This feature is available in this release as 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 . 1.2. Prerequisites for using separate heat stacks Your environment must meet the following prerequisites before you create a deployment using separate heat stacks: A working Red Hat OpenStack Platform 16 undercloud. For Ceph Storage users: access to Red Hat Ceph Storage 4. For the central location: three nodes that are capable of serving as central Controller nodes. All three Controller nodes must be in the same heat stack. You cannot split Controller nodes, or any of the control plane services, across separate heat stacks. For the distributed compute node (DCN) site: three nodes that are capable of serving as hyper-converged infrastructure (HCI) Compute nodes or standard compute nodes. For each additional DCN site: three HCI compute or Ceph nodes. All nodes must be pre-provisioned or able to PXE boot from the central deployment network. You can use a DHCP relay to enable this connectivity for DCNs. All nodes have been introspected by ironic. 1.3. Limitations of the example separate heat stacks deployment This document provides an example deployment that uses separate heat stacks on Red Hat OpenStack Platform. This example environment has the following limitations: Image service (glance) multi store is not currently available, but it is expected to be available in a future release. In the example in this guide, Block Storage (cinder) is the only service that uses Ceph Storage. Spine/Leaf networking - The example in this guide does not demonstrate any routing requirements. Routing requirements are found in most distributed compute node (DCN) deployments. Ironic DHCP Relay - This guide does not include how to configure ironic with a DHCP relay. Block Storage (cinder) active/active without Pacemaker is available as technical preview only. DCN HCI nodes are available as technical preview only.

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