Merging two ESXi host clusters in vCenter
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Merging two ESXi host clusters in vCenter

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Article ID: 402256

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Updated On:

Products

VMware vCenter Server

Issue/Introduction

Consolidate resources by merging two distinct ESXi host clusters within the same vCenter Server environment. This process facilitates improved manageability and resource optimization, such as merging a Cluster-A and a Cluster-B into a single production entity. This guide covers pre-checks for EVC compatibility, networking alignment, and the safe migration of hosts.

Environment

  • VMware vCenter Server 8.x
  • VMware ESXi 8.x

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:

Prerequisites and Pre-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 virtual switches (vDS) and port group names across both clusters to ensure VMs maintain connectivity after migration.

  • 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.

Recommended Steps for Cluster Merge

  • Disable High Availability (HA) and Distributed Resource Scheduler (DRS) on the source cluster.
  • Migrate or power off virtual machines hosted on source cluster nodes.
  • Place the ESXi host in Maintenance Mode.

Note: HA will not protect VMs while a host is in maintenance mode during migration.

  • Remove hosts from the source cluster while keeping them in vCenter inventory.
  • Add hosts to the Destination cluster.
  • Reconfigure networking (vDS or vSS) and storage (vSAN or datastores) as needed.
  • 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.

 

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