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 vSphere ESXi 6.x

VMware vCenter Server 8.x

VMware vCenter Server 7.x

VMware vCenter Server 6.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.
    
5. Right-click the virtual machine and click Edit Settings.

6. 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.

7. 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

For virtual machines that are configured with Microsoft Clustering Services:

1. Power off both virtual machines.
2. Right-click the Node B virtual machine and click Edit Settings.
3. Note the SCSI device that the RDM is using. For example, SCSI 0:5.
4. Remove the RDM hard disk from the virtual machine, ensure that the Delete from Disk option is not selected, and click OK.
5. Right-click the Node A virtual machine and click Edit Settings.
6. Note the SCSI device that the RDM is using. For example, SCSI 0:5.
7. Remove the RDM hard disk from the virtual machine, ensuring that the Delete from Disk option is selected, and click OK.
   
   Note: Unlike VMDK files, the Delete from Disk option removes only the RDM pointer files. Data on the RDM remains intact.
    
8. Right-click the Node A virtual machine and click Edit Settings.
9. Add the RDM 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 need in step 6.
10. Right-click the Node B virtual machine and click Edit Settings.
11. Add the RDM back to the virtual machine as an existing disk (use the RDM pointer file created in step 9) and select virtual compatibility mode. Ensure that you use the SCSI device that you need in step 3.
12. Power on the Node A virtual machine.
13. Power on the Node B virtual machine.