I learnt the hard way by putting everything on larger drives. I had a 5 TB die on me, completely full. 80% of everything that was on it was still to be watched. Thankfully, I had a friend at that stage that also kept everything archived. So I have chosen to use 2 and 3 TB Hard drives. Still it sucks to loose a lot of your stuff, specially if you have not watched it yet.
*EDIT*
Also to everyone else reading this thread
WATCH DEATH PARADE, IT IS ONE OF THE BEST ANIME I HAVE EVER SEEN*
*Even if you do not really like anime, I recommend that you watch it