Move physical RDM to a datastore

[joebrug]

I have an old FC SAN that contains physical RDMs that are attached as secondary drives to some VMs, various OS's (windows/linux, etc). Trying to migrate them to a new iSCSI san. The OS drives were on datastores on the old san, I have moved those to the new SAN, but the "data" RDMs still remain on the old one.  Yesterday, I powered down a VM, and read somewhere that you can cold storage vmotion the RDM to a new datastore and it will convert itself properly.  This was 1TB of data that took about 4 hours and seemed to be working and almost done.. but at the end, I got an error that popped up in vcenter that said "incompatible device backing specified for device '0'" .. that was it.. the 'destination' datastore was empty after this error.. VM still works on the old SAN.  I don't know how to avoid this error or what can be done to make the transfer work properly.

Let me know if something isn't clear, please.

[f10]

Hi,

I would suggest that you take a look at Migrating RDMs, and a question for RDM Users. | VMware vSphere Blog - VMware Blogs to understand the possibilities when using RDMs (Physical or Virtual compatibility) mode. If you cold migrate the RDM would be converted to a VMDK, do you want this option?

If not, you would have to use some kind of replication to copy the LUNs from old to new SAN.

-f10

http://highoncloud.blogspot.in/

About VMware Virtualization on NetApp

[joebrug]

Yes, my goal is to no longer use an RDM and to have it be a vmdk/datastore. I actually read that post yesterday, which is what gave me the idea of the cold migration. This portion, particularly:

VM with Physical (Pass-Thru) RDMs (Powered Off – Cold Migration):

• On a migrate, if I chose to change the format (via the advanced view), the pRDM is converted to a VMDK on the destination VMFS datastore.
• If I chose not to do any conversion, only the pRDM mapping file is moved from the source VMFS datastore to the destination VMFS datastore – the data stays on the original LUN

.

Like I said, it was definitely copying a ton of data over. I could see the old SAN and new SAN transferring lots of data for a number of hours, then noticed the data transfer basically stopped for about 10 mins, then that error popped up.  I assume it was done copying data and then the error popped up shortly thereafter

[mattisdabomb]

Hi There,

I am also having exactly the same problem. I'm using ESXi 5.1.

I have checked the CDROM drive does not have an ISO attached

Did you manage to resolve the problem?

Thanks

Matt

[joebrug]

I also used guest based mirroring to get rid of RDM's.. linux, windows, and netware. Wh33ly's steps are great.  Similar situation with the other operating systems depending on how the disks are set up :smileyhappy: but mirroring is the way to go.. plus, very little downtime if done right!

[markdjones82]

You can convert your RDM to virtual mode and then do a migration with storage vmotion.  I did this with many VM's

[Wh33ly]

The way I got rid of those annoying RDMs was with the use of the OS mirroring options.

In simple steps, add another VMDK with the same size as the RDM to the VM, create a mirror, resync, break mirror, remove RDM.

These steps I used on Windows machines

- Start with adding a VMDK disk with the same size as the RDM you want to get rid off

- Initialize disk VMDK disk in disk manager

- Convert the source disk to "Dynamic" (check permissions and shares beforehand because I noticed a few cases where they were removed when converting the disk to dynamic)

- Right click on the existing RDM volume and choose "Add Mirror"

- Choose the VMDK disk to add to the mirror  (this is probably the only option)

- If done right, the disks now start to resync, when there is a lot of data this can take a while. If the resync is complete both disks will show the state "Healthy" instead of "Resynching"

- Now it's time to remove the mirror as the disks are in sync

- Right click the mirrored volume and choose the option "Break Mirrored Volume" (this option will leave you with 2 identical disks which you can use), the option "Remove mirror" will destroy the mirror and 1 disk will not be usable.

- Change the drive letter(s) from the VMDK disk to the one of the RDM one.

- Remove the RDM disk from the VM through "Edit settings"

- Remove LUN from SAN

In our Linux environment we used the similar approach, but in that case the Linux admins handled it and didn't hear any issues so can't give you much tips on that one. I hope this helps you get rid of the RDM's :smileyhappy:

[Vikas Shitole]

VMware KB: Migrating virtual machines with Raw Device Mappings (RDMs)

This KB gives all the supported RDM migration options.

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