VMware & HP 3PAR – RDM disks and HP 3PAR snapshot

I will show you how you can take a cold snapshot via the HP 3PAR of a VMware RDM disk in physical compatibility mode. You can also do the snapshot while the guest host is running.

Check the guest hard disk and make a note of the vml file as seen in the screenshot as this will be needed to make sure all your RDM disks pointing to the correct vml file alter.

guest RDM disk

Here you will see that there are some files and folders in the RDM disk before the snapshot. Take a look at the date and time stamp of the files/folder.

Guest disk status before snapshot

Just check LUN is showing up on the ESX hosts, pay attention to the LUN ID and the naa (Network Addressing Authority) number to make sure you get the same one back from the SAN when you roll back the snapshot.

ESXi - Attached LUN

Now shutdown the guest machine.

ESXi - Guest shutdown

Now go to you InForm Manager console and take the snapshot. Give the destination volume a name, leave the ID ticked and then choose your snapshot option RO – Read Only or RW – Read/Write.

HP 3PAR - Taking a snapshot

I took a RO snapshot as shown below.

HP 3PAR - Snapshot

Now you can power up your guest machine and make any modification to the RDM disk, I decided to delete all the files and folder.

guest deleted file and folders

If you try to go into the InForm manager console and try to “promote” the RO snapshot you will see that the “promote” is grayed out. This is because the base volume is still exported to the ESXi hosts.

HP 3PAR - RO promote grayed out

So you don’t cause any issue with disk activity; shutdown the guest machine.


As an engineer I will do the following to avoid any issues with guest disk, ESX pointers, 3PAR ID allocation.

I would remove the disk from guest machine but not delete them, then I will detach the LUN’s from the hosts and then finally unexport the LUN’s in 3PAR.

To tell you the truth I took the risk and unexported the LUN in 3PAR.

HP 3PAR - unexport LUN

Now you will see that the RO snapshot is “promote” is not grayed out. Now “promote” the snapshot back into the base volume.

HP 3PAR - RO promote showing now

HP 3PAR - promte snapshot back to base volume

You will notice that the ESX hosts have lost connection to the LUNS, don’t worry about that.

ESXi - LUN detached

Once the snapshot has been committed back to the base volume it’s time to “export” the LUN back again to the ESX hosts. When you right click on the volume and go promote the default settings will be selected for you.

HP 3PAR - Exporting LUN again

Click next and choose “host set” if you have that set up, select the host set from the list and then don’t forget to untick the “auto” and put in the correct LUN ID, otherwise 3PAR will allocate any number which in my case it would of been “0”. Because 3PAR is not intelligent enough to take the LUN ID automatically. Click “finish” at the next dialog window.

HP 3PAR - Exporting LUN again 2

You will have to wait until all the ESX hosts see the LUN again under Storage Adapters settings.

For sanity I will allow all the ESX hosts to see the LUN again before you attempt to power up the guest machine.

The roll back of the snapshot has worked as you can see the files and folders are back to their original state.

Guest disk status before snapshot

Posted on January 19, 2013, in 3PAR, ESXi 4x & 5x, HP, VMware and tagged , , , , , , , . Bookmark the permalink. Leave a comment.

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