flips, the 20GB reference is just the size of the partition. That’s the size WHS v1 requires the OS partition to be, so it creates that and the rest of the drive becomes the D: partition.
As far as unraid goes, their website says it only supports up to 21 drives with the Pro license. shadowhc is talking about 25+ drives, so unless I’m misreading their website, unraid won’t work for his situation.