How to Upgrade VM Hardware Version of VMs Attached with RDM Disks.

Products

• VMware vSphere ESXi

Issue/Introduction

Guidance on upgrading the virtual machine (VM) hardware version to VMX-21 or recent for VMs that currently have RDM disks attached. The challenge arises because VMs configured with Physical RDMs (pRDMs) cannot use standard VMware snapshot functionality, which impacts the hardware upgrade workflow.

Environment

VMware vSphere ESXi 8.x

Cause

Physical RDMs (pRDMs) do not support VMware snapshots. Since upgrading a VM’s hardware version requires the ability to snapshot or otherwise protect the VM, the presence of pRDM disks blocks the hardware upgrade process. This is a known limitation documented in VMware KB 323064.

Resolution

• Detach RDM Disks Before Upgrade

  • Remove the pRDM disks from the VM.

  • After detaching, take a vCenter snapshot or backup to protect the VM.

  • Proceed with upgrading the VM Hardware Version to the latest.

  • Reattach the RDM disks once the upgrade is complete.

• Alternative Snapshot/Backup Options

  • Engage storage vendors to perform SAN-level snapshots of the RDM LUNs.

  • Alternatively, perform LUN-level or VMDK-level backups using third-party tools capable of handling VMDK-level protection.

 

Additional Information

• VMs using pRDMs cannot leverage VMware’s native snapshot capabilities.

• Backup operations must be carried out using external solutions or storage-based snapshot technologies.

• Engage storage vendors to explore feasible solutions and determine a suitable workflow.