How many hosts are required to set up a highly available Kubernetes cluster when using an external etcd topology?

Two control plane nodes and two etcd nodes are not sufficient for high availability with an external etcd setup; both would lack quorum if one node failed. A minimum of three is required for fault tolerance in a distributed system.

One control plane node is not highly available, representing a single point of failure, even if the etcd cluster has three nodes.

Combining control plane and etcd roles on three hosts describes a stacked etcd topology, not an external etcd topology, and doesn't match the six-host requirement for an external HA setup.

A highly available Kubernetes cluster requires a minimum of three control plane nodes for redundant API servers, schedulers, and controllers. For an external etcd topology, etcd also needs to run on at least three separate hosts to maintain quorum and fault tolerance, making a total of six distinct hosts the minimum for high availability.