asustor as6604t adding drives later?

[mrex]

If i start the nas with two 4-8tb drives at the beginning (raid1) and leave bays 3 and 4 empty, can i later add drives to the bays 4 and 5 (without loosing data from bays 1 and 2or do something wierd and complicated stuff)?

Im want mirrored drives - if one fails (from two), there is always one working drive (raid1). So finally i will have 4 drives 2x4-8tb condiguration. Im not even sure how this is done. Or is just bays 1-2 are paired (raid1) as a volume1 and later when i buy two more drives, i do the same, bays 3-4 are paired (raid1) as a volume2?

[orion]

ADM supports volume expansion: https://www.asustor.com/en-gb/online/Co ... ?topic=352. You can upgrade RAID-1 (2 disks) to RAID-3 (3 or more disks). It's online migration, so you don't need to shutdown NAS. (Note: the new disk size should be equal to or larger than the old disks.)

Yes, it's another way to create volume-2 with RAID-1 using bay-3 and bay-4. However the capacity is larger if you migrate to RAID-5 (4 disks).