Masters and Nodes
A Kubernetes cluster is made of masters and nodes. These are Linux hosts that can be VMs, bare metal servers in your data center, or instances in a private or public cloud.
Masters (Control Plane)
A Kubernetes master is a collection of system services that make up the control plane of the cluster.
The simplest setups run all the master services on a single host. However, this is only suitable for labs and test environments. For production environments, multi-master high availability (HA) is a must-have. This is why the major cloud providers implement HA masters as part of their Kubernetes-as-a-Service platforms, such as Azure Kubernetes Service (AKS), AWS Elastic Kubernetes Service (EKS), and Google Kubernetes Engine (GKE).
Generally speaking, running three or five replicated masters in an HA configuration is recommended.
It's also considered good practice not to run user applications on masters. This allows masters to concentrate entirely on managing...