What happens with data on RDMs once they are Storage migrated to VMDKs ?

[justme00]

Hello all,

  Given the next scenario : I have a VM with virtual RDMs. I storage migrate it online , selecting thick disks , therefore converting the RDMS to vmdks . The question is : what actually happens with the data on the Luns that were RDMs, once the migration is complete ?

  I would expect that the data is still there , and in case of need, I can remove the VMDKs and re-attach the luns again as RDMs. . But I can't find any official information on this .

Am I mistaken ? Is there somewhere that clearly mentions what happens with the data ?

Thank you !

[a_p_ · Accepted solution]

Your expectation is absolutely correct. The data on the raw LUN won't get touched after it is converted to a VM. Only the RDM mapping file is deleted and the LUN is available again, and you can use it to either map it again as an RDM or to create a VMFS datastore on it.

André

[continuum]

> I would expect that the data is still there , and in case of need, I can remove the VMDKs and re-attach the luns again as RDMs.

Just to be sure .... as soon as you start using the vmdks the data in the RDMs will become outdated.
So if you remove the vmdks in 2 weeks and switch that VM back to the RDMs 2 weeks of data will be missing.

To write those 2 weeks of data back to the RDM you would need to use extra steps before removing the vmdks.

[justme00]

Yes , that was clear that the data on RDMs would no longer be up to date once you modify data on vmdks.

Thank you.

[alunkal]

HI,

if we are converting a RDM  disk to vmdk,actually  what is happening?

whether the mapping file of the lun will get convert to vmdk file or the complete lun containing data will be converted to vmdk file?

i am little confused with the concept.

please advise

rgds

ritchie

[continuum]

Do you know the Linux dd command ?
What happens here is the same as you would get, when you dump a disk to a file.
dd if=physical-LUN of=flat.vmdk
only difference is that in this case the process also creates the vmdk-descriptor textfile

Regard the mapping file as something like a hardlink

[alunkal]

thanks for your reply.i got your point.