I bought a 2 TB WD My Cloud and works with a 1TB My Passport drive. Both were working fine but My Cloud stopped serving randomly… so I just had to reboot in order to get the service working again.
I noticed that if I un-plug the attached USB 3.0 drive then MyCloud works perfect… for days.
So my solution was to replace the power source (12V 1500 mA) for a better one (12V 5Amp ) and both re working now without disconnections.
WARNING: You need to be careful on choosing the proper power source. It MUST be a 12V and triple-check the correct polarity of the connections. If you do it wrong you can damage the product.
I hope this helps to all of you who are experiencing problems with the My Cloud unit. It is an excellent product but WD should provide a better power source for it.