How to force offline a virtual disk without data loss?

I have a H730P mini controller with some vdisks created. 

Assume that I do not want to shutdown the server, and host OS is not writing to the vdisk.

How to force offline one specific vdisk?  I can only do omconfig storage action to offline a pdisk, but not a vdisk. I have tried action=deletevdisk, but later when I recreate the vdisk, the data is gone. My intention is to gracefully migrate this vdisk to another server, or save the related pdisks for re-import the raid in the future.

Thanks!

Harley