Storage vMotion with RDMs on VMs

when you are performing Storage vMotion operations on a VM with at least one RDM and you want/need to convert your virtual disks from thick to thin (or vice versa) during the migration, you need to perform two (2) separate Storage vMotion operations:

1. First, you’ll migrate only the virtual disks attached to the VM. You’ll use the Advanced button when selecting the datastore so that you can leave the RDM alone for this migration. You’ll then select the appropriate format (“Thin Provisioned Format” or “Thick Format”) for the virtual disks on the target datastore and proceed with the Storage vMotion operation.