u/Soggy_Bid_3634

I've looked all over, and can't find documentation on this, so please direct me if there's a post somewhere about this.

I have a D2-320 in RAID 1 with two 8 TB drives, on a Mac.

If I replace them one at a time with two 20 TB drives and let the RAID rebuild after each replacement, how do I expand the array to use the full 20 TB? Is it automatic, or is there an extra step?