Is resizing control plane nodes after installation supported in OpenShift 4?
Environment
- Red Hat OpenShift Container Platform (RHOCP)
- 4
Issue
- Is control plane (master) nodes resizing a supported day-2 operation?
- How more resources can be added to the control plane nodes without reinstalling the cluster?
Resolution
There could be different procedures depending on the installation type and the platform:
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OpenShift 4.12 introduced the control plane machine sets, which allows to manage control plane nodes in an easy way in most IPI installations. Refer to managing control plane machines for additional information (new supported platforms were added in different releases, so select the documentation for the specific version of the cluster).
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Refer to the article how to increase resources for worker and master nodes in RHOCP 4 for VMware for increasing memory resources for a VMWare OpenShift cluster.
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For OpenStack platform, refer to upgrading OpenShift master node resources hosted on OpenStack platform.
In currently supported OpenShift versions, a rolling update resizing for the control plane nodes (shut down one of the control plane nodes at a time, modify its memory and/or CPU, and start up again) is possible if the infrastructure allows it.
Cautions:
- Make sure that the rest of the masters are completely healthy before removing or shutting down one of them.
- Removing or shutting down a master may be a risky operation in an overloaded or unhealthy cluster. Open a support case if the cluster is in this situation and needs to increase the hardware of the control plane nodes and some additional guidance is required.
Root Cause
In currently supported OpenShift versions, a rolling update resizing for the control plane nodes is possible if the infrastructure allows it.
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