Answer:When you remove one of the two SATA HDDs, the system will recognize the left one as an abnormal array. Then, when you put a HDD back, the system will recognize the two HDDs as two abnormal arrays. That is why it shows a warning message to remind you that is not a normal RAID 1 (mirroring) array.
In order to solve it, please press "F10" during POST to get into MediaShield Utility and do the following steps to rebuild the array.

Step 1: Please go to the MediaShield Utility (Press F10) and choose one of the SATA HDD (array) in "Array list".


Step 2: Press "Enter" to get into the "Array Detail"


Step 3: Press "D" to delete this array.


Step 4: After you delete it, please go to "Array Detail" of the left Array.


Step 5: Press "R" (Rebuild) to get into "Select From Free Disk List"


Step 6: Press "A" then "Enter" to rebuild array.


Step 7: Finished.


Step 8: Press "Ctrl-X" to exit.