Deactivating Enhanced Linked Mode (ELM) in vCenter 9.0 (VVF)

Products

• VMware vCenter Server

Issue/Introduction

• Administrators attempt to separate a vCenter Server instance from an Enhanced Linked Mode (ELM) group using cmsso-util break-elm.
• The operation fails during the pre-check or execution phase.
• Error output may indicate: [Pre-check] Executing break ELM on local node... followed by failure.
• Standard break-elm fails because vCenter Server nodes are mapped to themselves and have no active replication partners within the SSO domain.

Environment

• VMware vCenter Server 9.0.x
• VMware vSphere Foundation (VVF)
• VMware Cloud Foundation (VCF)

Cause

The standard break-elm operation requires active replication partners to coordinate the topology change. If the vCenter node has already partially lost its replication partners or is incorrectly mapped only to itself, the utility cannot complete the automated break process.

Resolution

Perform the following steps to manually isolate the vCenter node by repointing it to its own domain.

Step 1: Pre-requisites

1. Take an offline snapshot of all vCenter Server VMs in the SSO domain simultaneously.
2. Ensure you have the Single Sign-On (SSO) administrator password.

Step 2: Standard ELM Deactivation

Attempt the standard deactivation first:

1. SSH to the vCenter Server.
2. Run the pre-check: cmsso-util break-elm --mode pre-check --password ####
3. If the pre-check passes, execute the break: cmsso-util break-elm --mode execute --password ####

Additional Information

For reference - Deactivate Enhanced Link Mode from vCenter Using the cmsso-util break-elm Utililty