I'm looking to buy some 20tb drives to upgrade my NAS. It currently hosts a 12x3tb striped mirror setup on Truenas Scale plugged into a NetApp DS4246 24 bay. It is backed up elsewhere.

With how large HDDs and even SSDs are getting I would only need a mirrored 20tb pair to cover my current data and have quite a bit of open space left yet. (Like double) Eventually it will grow though. My backup uses a Rosewill case with 15bays. It seems ridiculous to only put two drives in a 24bay shelf. Even if I use another Rosewill case and put 14 drives in it, in a striped mirror setup that is 140tb.

Is it worth using the extra power of the shelf vs just a Rosewill case and some lsi cards? I wouldn't even need the lsi cards just yet. I'm contemplating selling the shelf and current drives and replacing it with 4 20tb. A mirror on the main setup and a mirror on the backup in two Rosewill cases. I do realize I lose the redundant power supplies.

(I realize that people in the data hoarder category are in a different situation but I don't plan on having 140tb of data in the near future.)