I have both a DNS-323 (1.08) and bought a new DNS-321 (1.03)
Was trying to 'clone' a working RAID-1 pair from the DNS323 over to the 321.
Have 2 pair of identical 2TB WD drives.
I removed on drive from the 323 (simulating a failure), installed a new blank drive in the 323 and it is back online and working fine.
I took the drive I removed from the right slot of the 323, moved to 321.  The 321 functioned fine (I could see all the data on the 'degraded' raid1 array.
I then repeated this process with the left drives.  Took the left drive from the 323, inserted a new drive and the 323 again rebuilt itself.   
I now have both drives from the orginal 323 ready to install in the 321.  I installed them (skipping the formatting step), and the 321 went to work repairing the 'degraded array'.   Not sure why it needed to do anything, since they were orginally a paired array in the 323.  This took several hours and completed.  I rebooted the 321, and it repeated the repair a second time.   After it complete, the raid 1 volume shows as working fine, and i can access all the data.   
Now the problem.   Every time I access the web server page on the 321, it asks me if i want to format the newly installed drives.   If I press 'skip', all is well and I can continue any function properly.   I am nervous to leave the unit this way, one of these days I might accidentally press continue, and watch the drive pair get wiped out.
Any ideas what is going on here?