Hi,
Could you get a more detail?
(1)The NAS bootable or not bootable.
(2)Confirm current disk conduction healthy or bad.
If it is possible. please get two screen shot.
A1.NasNavigator2 showing any information
A2. Log in to WEB UI then navigate to "Diskmanagement" -> "Drive Proerties"
(3)The customer have not added disk2,disk3 and disk4 before. Slot2, Slot3, Slot4 are empty. Is that right?