Please check the following items:
1. Please make sure the RAIDTool and Firmware are up to date. 1a. For update procedures, please follow the instructions: CLICK HERE
2. Please make sure the connection’s Firewire400/Firewire800/USB2.0.
3. Create / Re-create the RAID via RAIDTool. Please make sure the RAIDTool and Firmware is up to date (check step 1).
4. If the above methods do not work, please try: 4a. Change the RAID Type to JBOD. 4b. Partition the two individual hard drives. 4c. After the partition is completed, please change the RAID type to the desired RAID. 4d. Partition the hard drive.
For instruction on partition via Disk Utility, please check: CLICK HERE