Hi there
Could you tell us the make, model and capacity of your hard disk(s), whether or not it has been previously partitioned or formatted and what firmware version your DNS-323 is running? This details will help us suggest possible solutions.
As a starter, you may want to try ensuring the drive(s) are OK by connecting them to a PC and running Seatools or similar to check them. You may also want to run Gparted or similar to remove any existing partitions on the drive(s) before inserting them in to the DNS-323.
Thanks.