The Ready Stack design helps you specify the infrastructure requirements for building an on-premises OpenShift Container Platform 4.6 solution for SAP Data Intelligence. The following figure illustrates the design:
Figure 3. OpenShift Container Platform 4.6 cluster design for SAP Data Intelligence
The Ready Stack design recognizes four host types that make up every OpenShift Container Platform cluster: a bootstrap node, control-plane nodes, compute nodes, and storage nodes.
The deployment process for the Ready Stack also requires a node called the Cluster System Admin Host (CSAH).
Note: Red Hat refers to the CSAH node as the management host in the deployment process.
The CSAH node is required for OpenShift cluster administration, but is not part of the cluster. The authentication tokens that are needed to administer the OpenShift cluster are installed on the CSAH node only as part of the deployment process, whereas the OpenShift CLI administration tools are deployed onto the control-plane nodes. Dell Technologies strongly discourages connecting to a control-plane node to manage the cluster.
Note: Control-plane nodes are deployed using immutable infrastructure, further driving the preference for an administration host that is external to the cluster.
The CSAH node is used to manage the operation and installation of the container ecosystem cluster. Installation of the cluster begins with the creation of a bootstrap virtual machine (VM) on the CSAH node, which is used to install control-plane components on the controller nodes. Delete the bootstrap VM after the control plane is deployed. Dell Technologies recommends provisioning a dedicated host for administration of the OpenShift Container cluster. The initial minimum cluster can consist of three nodes running both the control plane and applications, or three control-plane nodes and at least two compute nodes. In both scenarios, OpenShift Container Platform requires three control-plane nodes.
Nodes that implement control-plane infrastructure management are called control-plane nodes. Three control-plane nodes establish the control plane for operation of an OpenShift cluster. The control plane operates outside the application container workloads and is responsible for ensuring the overall continued viability, health, availability, and integrity of the container ecosystem. The control plane can be made schedulable to enable SAP Data Intelligence workload on the control plane also. Removing control-plane nodes is not allowed.
In an OpenShift cluster, application containers are deployed to run on compute nodes by default. However, the term “compute node” is arbitrary; nothing specific is needed to run compute nodes and applications can also be run on control-plane nodes. Cluster nodes advertise their resources and resource utilization so that the scheduler can allocate containers and pods to these nodes and maintain a reasonable workload distribution.
Compute nodes can be added to or deleted from a cluster if doing so does not compromise the viability of the cluster. If the control-plane nodes are not designated as schedulable, at least two viable compute nodes must always be operating. Further, enough compute platform resources must be available to sustain the overall cluster application container workload.
Storage can be provisioned from dedicated nodes or shared with compute services. Provisioning occurs on disk drives that are locally attached to servers that have been added as compute nodes to the cluster.
OpenShift Container Storage, which is deployed after the cluster deployment, simplifies and automates the deployment of storage for cloud-native container use. To integrate Ceph-based OpenShift Container Storage into the container ecosystem infrastructure, administrators must provision appropriate storage nodes. As an alternative, they can use existing compute nodes if the nodes meet OpenShift Container Storage hardware requirements.
You can initiate the deployment of OpenShift Container Storage from the embedded OperatorHub when you are logged into OpenShift Container Platform as the cluster administrator. For more information, see the .
Note: Deployment of OpenShift Container Storage on a three-node compact cluster (control-plane nodes) is a Technology Preview feature. Red Hat does not recommend using Technology Preview features in production environments. Red Hat production service level agreements (SLAs) do not support these features and the features might not be functionally complete.
Dell has generated Ansible playbooks to fully prepare the CSAH node. Before the installation of the OpenShift Container Platform 4.6 cluster begins, the Ansible playbook sets up a PXE server, DHCP server, DNS server, HAProxy, and HTTP server. The playbook also creates ignition files to drive installation of the bootstrap, control-plane, and compute nodes and starts the bootstrap VM to initialize control-plane components. For more information, see the .