What is the minimum number of nodes required in a cluster architecture where some nodes perform control functions, and others deploy applications?

In a cluster architecture with role separation into control nodes (masters) and application deployment nodes (workers), the minimum number of nodes is usually 3.

This is due to the need to ensure fault tolerance and consensus among control nodes. For example, in Kubernetes, it is recommended to have an odd number of master nodes (at least 3) for proper operation of etcd and cluster management. For running applications, one or more worker nodes are sufficient.

Thus, the minimum configuration:

• 3 control nodes (for stability and to avoid split-brain)
• 1 or more nodes for applications

If we are talking about the very minimum cluster for testing, it can be just one node performing all roles, but for industrial operation, at least 3 nodes with role separation are required.