Convert large RDM to VMDK - what is the resulting size of the VMDK (and/or how to shrink/reclaim?)

[khurni]

We have a 9 TB RDM.

Only 3.13 TB of that is being used.

VMware Guest is Windows 2012 R2.

The "volume" in the OS is a single 9 TB volume.

So, when we convert the RDM to VMDK (either live via Storage vMotion, or we can do cold migrate/convert as well):

The KB indicates that the contents of the RDM are copied to a new underlying VMDK (on the destination).

What's not clear is:

a)  Assuming we leave everything as-is, does this make one large 9 TB VMDK?

b)  If so, what type?  Thick?  Thin?  Guessing Thick?

c)  Anyway to "shrink" the actual VMDK to say, 3.5 TB during the conversion/migrate process?

Unfortunately the data set is millions upon millions of 1-2kb files, so an OS file copy will take weeks.

I briefly wondered about using some sort of partition software to shrink the partition/volume (although Windows can do this natively AFAIK) to say, 3.5 TB, but that doesn't change the RDM size.

[SureshKumarMuth]

Hope this will help you

Comment by Andre

If you want to convert the RDM to a virtual disk with minimum downtime, you could simply shut down the VM, remove the pRDM from the VM, and re-attach it as a vRDM (using the same SCSI ID), and then power the VM on again. When you remove the pRDM from the VM, choose to delete the pRDM from the disk (this will only delete the mapping file), otherwise the raw LUN will not be available as a vRDM. After this you will be able to use Storage vMotion to migrate the VM. In order for the vRDM to be converted ino a virtual disk, you need to select a target virtual disk format (thick or thin) in the wizard, i.e. don't select "Same as source"!

Convert Physical Raw Device to VMDK

[a_p_ · Accepted solution]

in addition to the above mentioned comment, one of the following options should reduce the required disk space for the target virtual disk.

Zero out the empty space on the existing partition using e.g. sdelete, or - like you wrote - shrink the partition size from within the guest OS itself, create a temporary partition on the free disk space and zero it out. Then run Storage vMotion and select Thin Provisioning as the target virtual disk format.

André

[khurni]

Thank you everyone!

We'll see how the "shrinking" goes.

I'll report back, but our schedule isn't until 6/23/17 for this.

We thought that if we had the VM powered off it may make the storage vmotion go a little faster when converting the RDM to VMDK.

(Although also understood that if we convert the RDM from Physical that we could have "live" RDM to VMDK conversion as well).