Switching a VM disk of Raw Device Mapping(RDM) between physical and virtual compatibility modes in ESXi

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

This article provides steps to switch a VM disk of Raw Data Mapping (RDM) between physical and virtual compatibility modes without data loss.

Environment

VMware vSphere ESXi 8.x

VMware vSphere ESXi 7.x

VMware vCenter Server 8.x

VMware vCenter Server 7.x

Resolution

To change an RDM from physical to virtual compatibility mode:

Note: VMware recommends that you backup your configuration before performing these steps.

1. Power off the virtual machine.
2. Right-click the virtual machine and click Edit Settings.
3. Note the SCSI device that the RDM is using (for example, SCSI0:5).
4. Remove the RDM hard disk from the virtual machine, ensure that the Delete from Disk option is selected, and then click OK.
   
   Note: Unlike VMDK files, the Delete from Disk option removes only the RDM pointer files rdmp.vmdk. Data on the RDM remains intact.

Note: Per 8.0u3- These options are are "Remove Device" and "Remove Device and Data. Remove Device and Data is equivalent to the previous Delete from Disk.   The Remove Device simply removes the VMDK from the VMX but doesn't touch the .vmdk files.
 

1. Right-click the virtual machine and click Edit Settings.

2. Add the RDM back to the virtual machine as a new disk and select virtual compatibility mode (the naming of this option depends on the Esxi/Vcenter version used). Ensure that you use the SCSI device that you noted in step 3.

3. Power on the virtual machine.
   
   Note: An RDM can also be changed from virtual compatibility mode to physical compatibility mode. To change from virtual to physical compatibility mode, ensure there are no snapshots and select physical compatibility mode when completing step 6.

Note: If RDMs are bigger than 2TB you must use vSphere Web Client.

Additional Information

Supported storage configuration options for virtual machines configured with Microsoft Cluster Services (MSCS):   Supported Configuration Guidelines for Microsoft Windows Server Failover Clustering (WSFC) with shared disks