VMotion with RDM

[tropix]

hi all,

I'm wondering migrate some vmdk to RDM.

I found (here on forum community) two simple ways to do this:

\- using DD; and

\- using vmkfstools.

So, when I use a RDM, a vmdk metafile its created. This vmdk metafile must be stored on a VMFS, correct?

If I would use VMotion, this vmdk metafile must be stored on a VMFS that can be access by my all ESX servers?

Where is the size of vmdk metafile?

Regards,

Eduardo.

[Erik_Bussink]

I'm wondering migrate some vmdk to RDM.

I found (here on forum community) two simple ways to do this:

- using DD and using vmkfstools.

If you're VM is running Windows and you're RDM will contain the data disk of you're VM, you could also present a newly create RDM to the VM, and use microsoft's dynamic disk features to mirror/break/remove-physical volumes.

> So, when I use a RDM, a vmdk metafile its created. This vmdk metafile must be stored on a VMFS, correct?

Correct[/b]

.. VMotion, this vmdk metafile must be stored on a VMFS that can be access by my all ESX servers?

Correct[/b], both the metafile-vmfs and the RDM must be available to all ESX

Where is the size of vmdk metafile?

It's a small file, but if you check the size, it will show the file as the same size as the RDM.

Note: During ESX 2.5 we sometimes saw metafile links to RDMs get broken, and the only way to remove those broken links was to re-format the VMFS. Our strategy was to create a dedicated VMFS for RDM-Metafiles[/u] of about 100Mb. This way if we had some broken links it would not affect the normal VMFS.

[tropix]

Thanks Erik.

Yes, I think to create a VMFS to only store vmdk-rdm on my SAN. And I'll try to use microsoft feature of dynamic disk for WIndows VM.

But now I think in two another question. I have only one HBA (single port) on my ESX servers. Can I do this with one HBA?

And, I have actualy two vmdk, one where OS is installed and other to store data.

The disk that I want to migrate to RDM is the data disk. So if I want to use VMotion, I have to store the OS vmdk and the metafile vmdk in the same SAN VMFS?

Regards,

Eduardo

Message was edited by:

tropix

[Erik_Bussink · Accepted solution]

Tropix, you wrote

But now I think in two another question. I have only one HBA (single port) on my ESX servers. Can I do this with one HBA?

Yes. that should not be a problem.

And, I have actualy two vmdk, one where OS is installed and other to store data.

Make sure to keep your OS-system disk basic, but you will need to upgrade you're data disk to dynamic to play with the microsoft stripe volumes.

The disk that I want to migrate to RDM is the data disk. So if I want to use VMotion, I have to store the OS vmdk and the metafile vmdk in the same SAN VMFS?

No, keep VMDK on different LUNs is okay for Vmotion. As long as the 2nd ESX servers sees all LUNs (VMDK with system-disk, VMDK for MetaFile, RDM).

It's a shame that VMware hasn't updated this excellent ESX 2.5 document about Raw Device Mappings (RDM)

http://www.vmware.com/pdf/esx25_rawdevicemapping.pdf

[tropix]

Thanks about yours anwser Erik.

Eduardo