I have an unassigned 4TB WD Purple which I pass though to my Win10 VM for recording IP Cameras.
First thing is to get its device address. You want to use the device id as this remains persistent across reboots or if you rearrange your drives in your system.
Open the Unraid Terminal from the web GUI or SSH in if you prefer.
Navigate to /dev/disk/by-id/ and ‘ls’ to see all your physical disks and partitions.
In my case I am using a WD Purple 4TB which I know the model is WD40PURX. If you have more than one or are unsure, use the serial number to identify the correct disk.
Copy the entire name of the device which is NOT suffixed (i.e. not the -part1 or -part2 entries)
Next is to assign the unassigned drive to your VM so make sure your VM is shut down and then edit its settings.
You want to add a second vDisk location. Change to location to 'manual.
In the location entry section type “dev/disk/by-id/” and then paste the name of the disk you copied earlier.
Update the settings and start your VM. Winning.
P.S. Just as a reminder, unassigned disks are not protected by parity.