Attaching an RDM with snapshots to a virtual machine

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

This article provides the steps to add an RDM with snapshots to a virtual machine.

Environment

VMware ESXi 4.0.x Embedded
VMware ESXi 4.0.x Installable
VMware ESXi 4.1.x Installable
VMware ESX 4.0.x
VMware ESX 4.1.x
VMware ESXi 3.5.x Installable
VMware ESXi 4.1.x Embedded
VMware ESXi 3.5.x Embedded
VMware ESX Server 3.5.x

Resolution

To add an RDM with snapshots to a virtual machine:

1. Power down the virtual machine to which the RDM must be added.
2. In the vSphere Client, select the virtual machine and click Edit Settings.
3. Add a disk to the virtual machine and select the Raw Device Mapping option.
4. Point to the LUN to be used as the RDM.
5. Select Store with Virtual Machine.
6. Select Virtual Compatibility Mode.
7. Select the SCSI controller and SCSI ID for the RDM.
8. Click OK to save the settings.
9. Connect to the ESX host using an SSH session. 
10. Edit the descriptor file for the snapshot and ensure that it points to the RDM pointer file as the parent disk.
11. Note the parent CID within the descriptor file.
12. Edit the RDM Pointer file and change the CID information to match the parent CID information in the Snapshot Descriptor.
13. Edit the virtual machine's .vmx file and change the disk for the RDM to reference the snapshot file.
14. Unregister and re-register the virtual machine.
15. Power on the virtual machine and ensure that the data is intact.

Note: If you run virtual machines on snapshots for long periods of time, the snapshots may grow to the full size of the RDM if the number of changes is more.