Copying an RDM with VMKFSTOOLS

[sfortuna74]

Hello All -

Our situation is as follows: We have FC SAN that presents numerous datastores to our ESX 4.0 U1 environment. Our original datastore presentation was thick disk, however several months ago thin provisioning licenses were applied to our SAN appliance and we presented new, SAN-based thin provisioned datastores to our ESX cluster. Our goal was to move all vms from the SAN-thick datastores to the SAN-thin datastores. That was accomplished save for our vms which have RDMS in physical compatability mode - more or less a handful of MS clusters. What we have struggled with is how to move the RDMs from thick SAN to thin SAN. At the genius bar at VMworld, the person we spoke with explained that we would want to use VMKFSTOOLS for this exercise. Unfortunately, we didn't have enough time to write out the process as it would need to take place, so we are hoping someone could 1) confirm and perhaps 2) elaborate on the VMKFSTOOLS methodology to move our MSCS physical mode RDMS between thick and thin (SAN-based) datastores.

Thank you very, very much in advance -

Steve

[AssafSB · Accepted solution]

Hi Steve,

I'll try to help although I will say in advance I haven't tried it, this is just from what I read in the vmkfstools man.

From what I saw, there is a way to copy the data into an RDM LUN:

vmkfstools -i /vmfs/volumes/<VMDK-Directory>/<VMDK-Name>.vmdk -d rdmp:/vmfs/devices/disks/vml.<vml_ID>:0 /vmfs/volumes/<Destination-VMDK-Directory>/<Destination-VMDK-Name>.vmdk

The vml.<vml_ID> is basically a pointer to the disk identifier (wether it's an eui, naa or mpx). The easiest way I found to find which lun has which ID is through the vSphere client: Configuration>Storage>Devices and there you can match between the LUN and the Identifier fields. Than through the CLI you can run the following command to find the Identifier to vml mapping:

ls -l /vmfs/devices/disks/ | grep <Disk-Identifier>

You can than add the new disk by adding it through the vSphere Client as a regular existing disk. You will however need to do some operation on the MS cluster itself. In my opinion the best way is to shutdown the cluster, unmount the cluster disk, copy the RDM, remove the old RDM and mount the new one with the old one's mount point. I would also strongly recommend testing this before trying that on production servers.

Good luck, hope this helped you. Keep us updated on you progress with that

-Assaf