I remember my first mass storage device - a 10MB PC add-in card. My first thought -- I will never be able to fill that up! Last month I finished my do-it-yourself $1000** version of a $60,000 Kaleidescape video server (article to follow on how I did it). My system has a 6TB capacity Raid 5 drive using 8 one TB drives (if that does not add up, it is because one of the drives is configured as a hot spare). And the freaking thing is over 70% full already.
** This is, of course, if you treat my time as worth zero, especially for the process of ripping 400+ DVDs.