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  • Writer's pictureJJC Systems

Adding RDM Disk to a Virtual Machine (VM)

Objective: To provide step-by-step instructions for adding a Raw Device Mapping (RDM) disk to a virtual machine (VM) in a VMware environment.

Scope: This procedure applies to VMware vSphere environments and assumes familiarity with the VMware vSphere Client or vSphere Web Client.


1. Access to the VMware VMware VCenter.

2. Sufficient privileges to manage virtual machines and storage.

3. The RDM disk should be presented to the ESXi host where the VM resides.


1. Launch the VMware VCenter

2. Log in to the vCenter Server or the ESXi host where the VM is located.

3. Locate the virtual machine to which you want to add the RDM disk and ensure it is powered off. If it is powered on, shut it down gracefully.

4. Right-click on the virtual machine and select "Edit Settings" from the context menu. The Virtual Machine Properties window will appear.

5. In the Virtual Hardware tab, click the "Add" button to add a new device to the VM.

6. In the Add Hardware window, select "Hard Disk" and click "Next."

7. Choose "Raw Device Mappings"and click "Next."

8. Select the RDM LUN (Logical Unit Number) or disk from the list of available devices and click "Next."

9. Choose the compatibility mode for the RDM disk:

  • "Physical compatibility" mode provides full disk access but limits VMotion and snapshot functionalities.

  • "Virtual"compatibility mode allows for VMotion and snapshot functionalities but has some limitations.

10. Select the desired datastore where the RDM pointer file will be created. This file contains

metadata about the RDM disk and is required for VM management. Click "Next."

11. Specify the virtual device node for the RDM disk. You can either accept the default selection or choose a different SCSI adapter and bus number. Click "Next."

12. Review the configuration summary and click "Finish" to complete the RDM disk addition process.

13. Back in the Virtual Machine Properties window, click "OK" to save the changes.

14. Power on the virtual machine. The RDM disk should now be available to the VM.

Post-Configuration Steps:

1. Once the virtual machine is powered on, you can verify the presence of the RDM disk by

checking the operating system's disk management utility within the VM.

2. Format and partition the RDM disk as needed within the VM's operating system.

3. Ensure that proper backups and monitoring are in place for the newly added RDM disk.

4. Document the changes made, including the details of the added RDM disk, for future reference.

Conclusion: By following this SOP, you can successfully add a Raw Device Mapping (RDM) disk to a virtual machine (VM) in a VMware vSphere environment.

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