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?
| Component | Runs On | Purpose |
|---|---|---|
| vCenter | Management VM | Controls everything |
| Supervisor Control Plane | VMs | Cluster management |
| ESXi Hosts | Physical servers | Act as worker nodes |
| Spherelet | Inside ESXi | Runs workloads |
| VKS Cluster | VMs | Runs applications |
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
Disclaimer
This blog is for informational and educational purposes only. The configurations, examples, and architectural guidance provided are based on general best practices and publicly available references.
Always validate configurations in a non-production environment before applying them to live systems. Features and integrations may vary depending on the versions of VKS, VKr, LCI, Supervisor and vCenter Server being used. The author is not responsible for any unintended impact caused by the use of this information in production environments.
Contents, and opinions are my own and do not reflect the opinions of my employer.