vSphere Supervisor Cluster Overview

Introduction

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

• what exactly is it?
• Why do we need it?
• How does it actually work internally?

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

---

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

---

Why do we need vSphere 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 can't create VKS Cluster in vSphere.

---

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.

---

2. ESXi Hosts (Worker Nodes)

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

Instead of VM-based workers, ESXi hosts themselves act as worker nodes

---

3. Supervisor Control Plane (VMs)

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

Responsible for managing the cluster.

---

4. Spherelet (Inside ESXi)

• Special component inside ESXi
• Similar to Kubernetes kubelet

Responsible for:

• Communicating with control plane
• Running workloads on ESXi

Spherelet = kubelet for ESXi

---

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

---

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.

---

How vSphere 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.

---

Step 2: Supervisor Cluster Initialization

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

---

Step 3: vSphere Namespace Creation

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

---

Step 4: VKS Cluster Deployment

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

---

Step 5: Workloads Deployment

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

---

What Runs Where?

---

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