Scale Workload Clusters

This topic explains how to scale a workload cluster in two ways:

Scale horizontally: Scale the number of control plane and worker nodes. See Scale a Cluster Horizontally.
Scale vertically: Change the size of the control plane and worker nodes. See Scale a Cluster Vertically.

Note: To scale nodes in a node pool, see Update Node Pools in Manage Node Pools of Different VM Types.

Scale a Cluster Horizontally

You can horizontally scale a workload cluster in two ways:

Run the tanzu cluster scale command.
- The --controlplane-machine-count and --worker-machine-count options set the new number of control plane and worker nodes, respectively.
- Examples:
  - To scale a cluster to 5 control plane nodes and 10 worker nodes:
```
tanzu cluster scale MY-CLUSTER --controlplane-machine-count 5 --worker-machine-count 10
```
    If you deployed a cluster with --controlplane-machine-count 1 and then you scale it up to 3 control plane nodes, Tanzu Kubernetes Grid automatically enables stacked HA on the control plane.
  - If the cluster is running in a namespace other than default, you must include the --namespace option:
```
tanzu cluster scale MY-CLUSTER --controlplane-machine-count 5 --worker-machine-count 10 --namespace=MY-NAMESPACE
```
- Note: On clusters that run in vSphere with Tanzu, you can only run either 1 control plane node or 3 control plane nodes. You can scale up the number of control plane nodes from 1 to 3, but you cannot scale down the number from 3 to 1.
Important: Do not change context or edit the .kube-tkg/config file while Tanzu Kubernetes Grid operations are running.
Class-based clusters: Follow the Configuring Cluster Topology procedure to change the replicas settings under controlPlane and workers in the cluster definition.

How to vertically scale a workload cluster depends on the cluster type:

Class-based Clusters: Follow the Configuring Cluster Topology procedure to change the vmClass settings in the cluster definition.
TKC Clusters: Follow the Updating Infrastructure Machine Templates procedure in The Cluster API Book, which changes the cluster’s machine template.

The procedure downloads the cluster’s existing machine template, with a kubectl get command that you can construct as follows:
```
kubectl get MACHINE-TEMPLATE-TYPE MACHINE-TEMPLATE-NAME -o yaml
```
Where:
- MACHINE-TEMPLATE-TYPE is:
  - VsphereMachineTemplate on vSphere
  - AWSMachineTemplate on Amazon Web Services (AWS)
  - AzureMachineTemplate on Azure
- MACHINE-TEMPLATE-NAME is the name of the machine template for the cluster nodes that you are scaling, which follows the form:
  - CLUSTER-NAME-control-plane for control plane nodes
  - CLUSTER-NAME-worker for worker nodes
For example:
```
kubectl get VsphereMachineTemplate monitoring-cluster-worker -o yaml
```