There is no GUI option available to rename virtual disk in vmware. There was a request to add few RDM luns to a virtual machine and those disk to be renamed as per the standard they have (Combinatioin of LUN ID, storage Pool ID and disk size).
This request was accomplised using the steps followed below:
1. Add the provided RDM to the virtual machine.
2. Note the datastore where the disks were stored.
3. Remove those RDM from the virtual machine.
4. Find the ESX host on which the virtul machine resides.
5. Connect to the ESX host using Putty.
6. Navigate to the directory containing virtual machine (notes in Step 2).
7. cd /vmfs/volumes/DatastoreName/originalname
8. Once the required file is found, execute the below command
# vmkfstools -E “originalname.vmdk” “newname.vmdk”
9. Again add the vmdk uing an existing disk option.