have not used this previously, want to make sure I understand things early. I'm looking to make one of the cheap nas servers you see on youtube. if I shuck let's say 4 drives to create the array and 1 ssd for cache along with usb to load the os, what I'd like to know is how would be able to upgrade the array later? if the 4 drives is not enough or I decide to add more, how to expand the existing array to new drives?