Only one hard disk

Hallo,

Is it possible to run the Ex4 with only one harddisc inserted?

While i want to buy a new disc and i prefer to buy al large disc and then later buy anonther one at the same size. 

Is it also possible to run the Ex4 with two different harddisc (3Tb and 1TB)

Yes, you can use the drive with only one drive on it.

See if this anwers your second question

http://community.wd.com/t5/WD-My-Cloud-EX4/RAID-5-different-drive-sizes/m-p/718180#M1483