How to Merge Two Clusters in the Same vCenter

Products

• VMware vCenter Server

Issue/Introduction

Organizations may need to consolidate resources by merging two distinct ESXi host clusters within the same vCenter for improved manageability, resource optimization, or architectural changes.

Environment

VMware vCenter Server

Resolution

Merging clusters is a multi-step process requiring careful alignment of compute, networking, and storage configurations. Below is a step-by-step guide to perform the merge successfully:

Pre-Merge Checks

• CPU & EVC Compatibility: Ensure host hardware is compatible, especially Enhanced vMotion Compatibility (EVC).

• Licensing: Verify your vCenter license supports the total number of hosts and features like DRS, HA, and vSAN.

• Networking: Standardize VMkernel adapters and virtual switches across both clusters.

• Storage: For environments using vSAN, disk group reconfiguration may be required.

Note: While moving ESXi host (s) from Source Cluster to Destination Cluster . Ensure the Source Cluster has enough capacity to handle running VMs during host migration, or schedule downtime to power them off.

 

Merge Procedure

1. Disable HA and DRS on the source cluster.

2. Migrate or power off virtual machines hosted on source cluster nodes.

3. Place the ESXi host in Maintenance Mode.

4. Remove hosts from the source cluster while keeping them in vCenter inventory.

5. Add hosts to the Destination cluster.

6. Reconfigure networking (vDS or vSS) and storage (vSAN or datastores) as needed.

7. Enable HA and DRS on the updated cluster.

Additional Information

 

• If Distributed Virtual Switches (vDS) are used, export/import config between clusters.

Backing Up and Restoring a vSphere Distributed Switch Configuration

• For vSAN, disk reformat may be necessary on migrated hosts.

• Always perform backups or snapshots of vCenter before executing changes.