How to migrate VM from\TO Raw Device Mapping (RDM) (datastore)

[mostfaleoni]

Hello All,

Could i aske about How to migrate VM from\TO Raw Device Mapping (RDM) (datastore)?

Thanks all for your support

[vGuy]

Can you elaborate a bit more...do you have a VM with RDM that you would like to SvMotion to another Datastore?

[mostfaleoni]

Yes i have VM i need SvMotion to another Datastore and after i finsh i need to return back to the RDM

Thanks for your support.

[marcelo_soares]

If you have a VM that have RDMs and VMDKs and you svmotion it, the VMDKs will be moved and the RDM pointers will be also. The pointers will stillp point the correct LUNs, sou you don't need to worry about it. No dettach/attach operation is needed.

[vGuy · Accepted solution]

If you're using vSphere 5, then you can SvMotion the VM attached to an RDM (both physical or virtual) with no issues. Meaning only RDM mapping file will be moved from one Datastore to another without any changes/conversion to the actual RDM disk.

Note: Do not try to modify the disk format thin or thick as it will cause the RDM disk to be converter to virtual disk.

More info here: http://blogs.vmware.com/vsphere/2012/02/migrating-rdms-and-a-question-for-rdm-users.html

If vSphere 4.x is used, then hot migrating the VM to another Datastore will not change the format of the RDM, only mapping file will be moved. This is true for both virtual and physical RDM.

However, cold migrating the VM to another Datatore will change the RDM to virtual disk format.

hth...let me know if you have any questions..

[mostfaleoni]

Hello,

burt if i need to go back to RDM datastore how can i do this becuase the  RDM datastore not listed on my datastore also what do you meen about hot migrating is it the normal way for migrating.

also i would say thanks for marcelo.soares & vGuy

[vGuy]

mostfaleoni wrote:

Hello,

burt if i need to go back to RDM datastore how can i do this becuase the  RDM datastore not listed on my datastore also what do you meen about hot migrating is it the normal way for migrating.

also i would say thanks for marcelo.soares & vGuy

RDM disk is stored on the external storage and only it's mapping file is stored on a VMFS Datastore. When you SvMotion the VM containing RDM to another Datastore, a) virtual disks are moved to the new Datastore b) RDM mapping file is moved to the new Datastore. No manual intervention/copying is required.

Hot migration refers to migrating the VM while it's powered ON.

And Cold migration refers to migrating the VM while it's power OFF.

for your reading pleasure: http://www.virtuallifestyle.nl/2010/01/recommended-detailed-material-on-rdms/