Can I add external drive to My Cloud NAS?

I have a 4TB My Cloud drive. I’d like to expand the storage. Can I attach a USB external hard drive to it such as a My Book drive? I saw an 8TB Seagate Backup Plus drive I’d like to get, but only if I can attach it to the NAS.

Anyone have any experience with this? Does it work well?

Have you read the My Cloud User Manual ( If not you should, it explains adding a USB drive for extra storage and or to use as a backup location.

For anyone looking for this in the future, here is a video I found explaining the process. Adding a USB Drive to the Personal Cloud - YouTube