Yes you can replace the hard drive that ships with the My Cloud with another drive. There are a variety of threads/posts that detail the “unbricking” process that is used when one replaces the hard drive. I did the same. Replaced a non functioning 4T drive with, first a spare 250GB drive I had laying around, then replaced the 250GB drive with a 1T drive that is in the WD My Cloud enclosure currently. Some of us have had problems with the Dashboard not working properly (or not showing at all) after unbricking then upgrading to the latest firmware.
Do a forum search for “unbricking” and you’ll find several threads with various methods used. I detail my steps at the following link that worked for me to unbrick then fix the no Dashboard issue. No guarantee it will work for others.
https://community.wd.com/t/unbrick-then-firmware-upgrade-equals-no-dashboard/136666/6?u=bennor
