When attempting to add a Raw Device Mapping (RDM) to the VMs, the Target LUN list appears empty.

Products

• VMware vSphere ESXi

Issue/Introduction

After migrating two VMs participating in a Microsoft cluster service between clusters, the RDM LUNs cannot be re-added to the primary VM.
Although the LUNs are visible as "Connected" in the ESXi storage device list, the "Target LUN" selection dialog remains empty during the "Add New RDM Disk" wizard.

Environment

VMware ESXi 8.x

Cause

The migration of clustered virtual machines with Raw Device Mappings was performed without following mandatory shared storage migration procedures, resulting in stale locks or incorrect device registration.

Resolution

To restore the shared RDM configuration, perform the following steps:

• Ensure the RDM pointer file is completely removed from all secondary cluster nodes.
  
  
• Perform a Rescan Storage and Rescan Adapter on all ESXi hosts within the cluster to refresh LUN availability and clear stale metadata/locks.
  
  
• Right-click the Primary VM > Edit Settings > Add New Device > RDM Disk.
  
  
• Select the desired Target LUN (now visible) and complete the wizard.
  
  
• On the Secondary VM, select Add New Device > Existing Hard Disk.
  
  
• Navigate to the Primary VM's datastore directory and select the .vmdk RDM pointer file created in Step 3.

Additional Information

Migrating virtual machines with Raw Device Mappings (RDMs) from one vSphere Cluster to another