Here is what I did.
I shut down the dns-323.
I removed the left 1TB drive and inserted a 2TB drive.
I powered on the DNS-323
I formatted the 2TB drive
I shut down the DNS-323
I removed the 2TB drive and replaced the original 1TB drive
I powered on the DNS-323
Quite honestly, I don't see how doing something like this should mean a complete backup of the drive. I haven't done anything destructive. Merely removing and replacing a drive with proper shutdowns shouldn't be a danger to data integrity. I can't even count the number of times I've swapped out SATA drives in my PC's over the years.
Regardless, the DNS-323 is now asking me to click NEXT or SKIP for this 1TB drive. If I click next, can I be assured the drive will NOT be formatted? BTW, the other drive can be seen and accessed just fine.