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OCPBUGS-114888: Updated exactly three control plane nodes must be to m… #119021

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2 changes: 1 addition & 1 deletion modules/architecture-machine-roles.adoc
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Expand Up @@ -98,7 +98,7 @@ Extra controls apply to control plane machines to prevent you from deleting all
[NOTE]
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ifndef::openshift-dedicated,openshift-rosa[]
Exactly three control plane nodes must be used for all production deployments. However, on bare metal platforms, clusters can be scaled up to five control plane nodes.
Exactly three control plane nodes must be used for all production deployments. On a bare-metal platform, you can scale a cluster to three, four, or five control plane nodes.
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@hasbro17 hasbro17 Aug 31, 2026

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The etcd cluster size must be odd. Even cluster sizes like 4 have a worse fault tolerance than 3 since more nodes can fail to get us to quorum loss.
https://etcd.io/docs/v3.7/faq/#why-an-odd-number-of-cluster-members

So we should only recommend odd sizes: 3 and 5.

endif::openshift-dedicated,openshift-rosa[]
ifdef::openshift-dedicated,openshift-rosa[]
Single availability zone clusters and multiple availability zone clusters require a minimum of three control plane nodes.
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