Chapter 4. Planning your Environment

The Red Hat Enterprise Linux OpenStack Platform installer maps OpenStack services to hosts in your environment and installs these services to their assigned hosts. This includes various options for high-availability controllers, Neutron or Nova networking, and a choice of messaging service. A deployment also provides specific parameters to customize each service. This provides a mechanism to define all aspects of an OpenStack environment and help scale the environment in the future.
Prior to creating a deployment, plan how your environment looks so that you can correctly define the various host roles and services.
The following diagram outlines the topology of a sample deployment, which this chapter examines in greater detail:
Sample Deployment Topology

Figure 4.1. Sample Deployment Topology

4.1. Hosts

Before you create a deployment, assign a role to each host and ensure each host meets the requirements set in Section 2.3, “Host Requirements”.
The RHEL OpenStack Plaform installer uses four roles:
Controller
Provides key services such as the MySQL database for storing data about your environment, Horizon, Keystone, and Glance.
Compute
A host that acts as a hypervisor, providing the processing capabilities required for running virtual machines in the environment. You can add more Compute nodes to your environment at any time by assigning additional hosts to this deployment role and repeating the provisioning process; the installer ignores all hosts that have already been provisioned and provisions only the new host.
Ceph Storage Node (OSD)
A generic Red Hat Enterprise Linux 7.2 host that can be manually configured after deployment to act as a Ceph storage server node. This deployment role is optional.
Generic RHEL 7
A generic Red Hat Enterprise Linux 7.2 host that can be manually configured after deployment to provide services not defined by any of the pre-existing deployment roles. This deployment role is optional.
In Figure 4.1, “Sample Deployment Topology”, there are seven hosts in the deployment. The server icon at the top of the diagram represents the installer. The server icon beneath the installer represents controller nodes. Because this deployment uses high availability, there are three hosts assigned to this role so that the environment can continue to function in the event of a failure on any of the three nodes. The three server icons directly beneath the controller nodes represent compute nodes. The first two compute nodes were added when the RHEL OpenStack Platform environment was provisioned. The third compute node, Compute N, represents additional compute nodes that can be added to the environment after it has been provisioned to enable horizontal scaling. The final server icon in the diagram represents a Ceph OSD node.