Using 8TB Thunderbolt Duo drive to backup photos from iMac 3TB drive. 8TB drive is set up as Raid 1 (4 TB mirror drive). I’m only backing up part of the 3TB drive (pictures only) why is WD drive showing full?
You should try contacting WD Support for such issue.
You can refer the link given below to contact them via phone or you can create a support case to get in-touch with WD Support.
Create a Support Case: