PERFECT, life is sooooooooooooo good.
I converted 2 standard HDDs into RAID1. After formating, I got a CLEAN, EMPTY volume.
I had backup important data. What I lost was just some movies. So never mind... I will copy them back from my friends.
What I learned is, maybe it is still possible to convert standard to RAID1 without losing data, but DO NOT take the Risk. If you think DLINK DNS 320 (firmware 2.02) is a mature product, you could convert to RAID1 without backup all your data, THINK AGAIN!