kubeadm: add improvements to HA docs (#11094)

* kubeadm: add information and diagrams for HA topologies

* kubeadm: update HA doc with simplified steps

* kubeadm: update HA doc with simplified steps

* edit ha, add new topology topic, reorder by weight

* troubleshoot markdown

* fix more markdown, fix links

* more markdown

* more markdown

* more markdown

* changes after reviewer comments

* add steps about Weave

* update note about stacked topology

content/en/docs/setup/independent/ha-topology.md

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+---
+reviewers:
+- sig-cluster-lifecycle
+title: Options for Highly Available Topology
+content_template: templates/concept
+weight: 50
+---
+
+{{% capture overview %}}
+
+This page explains the two options for configuring the topology of your highly available (HA) Kubernetes clusters.
+
+You can set up an HA cluster:
+
+- With stacked control plane nodes, where etcd nodes are colocated with control plane nodes
+- With external etcd nodes, where etcd runs on separate nodes from the control plane
+
+You should carefully consider the advantages and disadvantages of each topology before setting up an HA cluster.
+
+{{% /capture %}}
+
+{{% capture body %}}
+
+## Stacked etcd topology
+
+A stacked HA cluster is a [topology](https://en.wikipedia.org/wiki/Network_topology) where the distributed
+data storage cluster provided by etcd is stacked on top of the cluster formed by the nodes managed by
+kubeadm that run control plane components.
+
+Each control plane node runs an instance of the `kube-apiserver`, `kube-scheduler`, and `kube-controller-manager`.
+The `kube-apiserver` is exposed to worker nodes using a load balancer.
+
+Each control plane node creates a local etcd member and this etcd member communicate only with
+the `kube-apiserver` of this node. The same applies to the local `kube-controller-manager`
+and `kube-scheduler` instances.
+
+This topology couples the control planes and etcd members on the same nodes. It is simpler to set up than a cluster 
+with external etcd nodes, and simpler to manage for replication.
+
+However, a stacked cluster runs the risk of failed coupling. If one node goes down, both an etcd member and a control
+plane instance are lost, and redundancy is compromised. You can mitigate this risk by adding more control plane nodes.
+
+You should therefore run a minimum of three stacked control plane nodes for an HA cluster.
+
+This is the default topology in kubeadm. A local etcd member is created automatically
+on control plane nodes when using `kubeadm init` and `kubeadm join --experimental-control-plane`.
+
+![Stacked etcd topology](/images/kubeadm/kubeadm-ha-topology-stacked-etcd.svg)
+
+## External etcd topology
+
+An HA cluster with external etcd is a [topology](https://en.wikipedia.org/wiki/Network_topology) where the distributed data storage cluster provided by etcd is external to the cluster formed by the nodes that run control plane components.
+
+Like the stacked etcd topology, each control plane node in an external etcd topology runs an instance of the `kube-apiserver`, `kube-scheduler`, and `kube-controller-manager`. And the `kube-apiserver` is exposed to worker nodes using a load balancer. However, etcd members run on separate hosts, and each etcd host communicates with the `kube-apiserver` of each control plane node.
+
+This topology decouples the control plane and etcd member. It therefore provides an HA setup where
+losing a control plane instance or an etcd member has less impact and does not affect
+the cluster redundancy as much as the stacked HA topology.
+
+However, this topology requires twice the number of hosts as the stacked HA topology.
+A minimum of three hosts for control plane nodes and three hosts for etcd nodes are required for an HA cluster with this topology.
+
+![External etcd topology](/images/kubeadm/kubeadm-ha-topology-external-etcd.svg)
+
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+- [Set up a highly available cluster with kubeadm](/docs/setup/independent/high-availability/)
+
+{{% /capture %}}