Some times I do hoard some data, usually after some harddisk change of something, in wich case i get a folder named olddisk with the contents of the old disk, this method does lead to having a bunch of such folders, like olddisk1 olddisk2 and so on, I usually take far too many photos on my trips so I end up with GIGs of photos, I can imagine a person who takes vidoes of everything would fill 20TB in a couple of years... anyway, im trying to lead this to a non piracy based all music and torrented video scenario. what I do,bear in mind that I only have 2 TB of stuff, is :
run a duplicate finder program,maybe you (ops, I meant your friend) have to much duplicate stuff.
if there are many videos, are they in the apropriate quality and sampling rate ? do your VHS tapes really need to be in 1080p ?
1) use a raid station to backup. I have a synology I use for bck.
2) keep the sdcards after they are full. I do not erase sd cards from my camera, I just store them remotelly, cheap baackup for one of the most precious and inpossible toreproduce files.
3) get 10 2TB hard disk to copy your stuff and store it :) I really cant visualise getting 20TB of data for a home user...