vSphere Supervisor Cluster Overview

Introduction

If you are starting with VMware vSphere and Kubernetes, one important concept you will hear is Supervisor Cluster.

But what exactly is it?
Why do we need it?
And how does it actually work internally?

In this guide, we will explain everything in simple language, along with a clear workflow.

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What is vSphere Supervisor Cluster?

The Supervisor Cluster is a special Kubernetes cluster that runs directly on ESXi hosts.

It enables Kubernetes inside vSphere.

Before Supervisor: vSphere runs Virtual Machines

After Supervisor: vSphere can run Kubernetes clusters as well

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Why Do We Need Supervisor Cluster?

Kubernetes and vSphere are different systems.

• vSphere manages infrastructure (VMs, storage, networking)
• Kubernetes manages containers (pods, services)

Supervisor acts as a bridge between vSphere and Kubernetes

Without Supervisor:

• You cannot create Kubernetes clusters in vSphere (VKS)

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High-Level Architecture

Key Components of Supervisor Cluster

1. vCenter Server (Management Layer)

• Central management system
• Enables Workload Management
• Deploys and manages Supervisor Cluster
• Handles lifecycle operations

Think of it as the brain of the platform

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2. ESXi Hosts (Worker Nodes)

• Physical servers running ESXi
• Act as Kubernetes worker nodes in Supervisor

Important:

Instead of VM-based workers:

• ESXi hosts themselves act as worker nodes

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3. Supervisor Control Plane (VMs)

• Deployed automatically as virtual machines
• Runs Kubernetes core components: -s API Server
  • Scheduler
  • Controller Manager
  • etcd

Responsible for managing the cluster

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4. Spherelet (Inside ESXi)

• Special component inside ESXi
• Similar to Kubernetes kubelet

Responsible for:

• Communicating with control plane
• Running workloads on ESXi

Simple definition: Spherelet = kubelet for ESXi

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5. vSphere Namespaces

• Logical resource boundaries inside Supervisor
• Used for organizing and isolating workloads

Each Namespace defines:

• CPU and memory limits
• Storage policies
• Access permissions

VKS Clusters(TKG Clusters, Guest Clusters), VM Service VMs, vSphere Pods are created inside Namespaces

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6. VKS Cluster (Guest Cluster)

• Full Kubernetes cluster created by Supervisor
• Runs as virtual machines

Contains:

• Control Plane Nodes (VMs)
• Worker Nodes (VMs)
• Application Pods

This is where actual applications run

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How Supervisor Cluster Works (Step-by-Step Workflow)

Step 1: Enable Workload Management

• User logs into vCenter
• Enables Workload Management
• Configures networking and storage

Supervisor Cluster gets deployed automatically

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Step 2: Supervisor Cluster Initialization

• Control Plane VMs are created
• ESXi hosts are registered as worker nodes
• Spherelet is activated

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Step 3: vSphere Namespace Creation

• Admin creates Namespace
• Assigns:
  • Resources
  • Storage policy
  • Permissions

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Step 4: VKS Cluster Deployment

• User submits YAML or uses vCenter UI
• Supervisor processes request
• Creates:
  • Control plane VMs
  • Worker node VMs

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Step 5: Workloads Deployment

• Developers access VKS cluster
• Deploy applications (pods, services)

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What Runs Where?

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Final Summary

• Supervisor Cluster brings Kubernetes into vSphere
• ESXi hosts act as worker nodes
• Control plane runs as VMs
• Spherelet replaces kubelet
• VKS clusters run applications

Next Article: Beginner Guide to VKS Cluster Overview