Each file server has two arrays, a "live" RAID5 array, and an array that stores the daily backup for one of the others (which is soft-RAID0, which I realize is a risk, but no moreso than making a JBOD, which was my other choice for 2-disk high capacity RAID...). Those machines each have a dedicated Gbit link to their replication partner and a second Gbit link to my switch. Works pretty well, especially since I don't have access to LTO or the like for a proper backup.
Several years ago I cobbled together some perl scripts that comb open file shares for files and folders that match specific naming conventions that I use. These let me automate moving things from individual computers to central storage on the file servers (2 for porn, one for non-porn video clips like downloaded TV shows, one for comics, pictures, ebooks, text files, office-type documents and audio files). I exempt video captures and DVD rips from that process, but everything else ultimately ends up on one of the big boxes. The shares on all the file servers are NSFmounted on one machine and are presented to my computers via Samba as a single namespace.
Why are there four machines? Because at one time, I was trying to achieve reasonable storage density with 80GB drives, and one and then two file servers simply were not adequate. Now I have staggering density, but that's because I've continuously upgraded those machines - 80s begat 160s begat 250s begat 400s.
I'm at about 80% utilization on the (actual) 3TB that are on those machines, and local storage on my desktop machines has therefore been growing quite a bit as well. Just over 2TB on my HTserver (recorded TV stuff), another 2.4TB on my game machine (DVD rips etc), miscellaneous removable drives... I could probably use the storage I have in a more efficient manner, but of course I'm very leery of not having at least a couple copies of anything that winds up on my storage servers.
I'm already using some 400GB drives. Next time I get a decent score from one of my contracting jobs I'll probably buy a bunch more. I don't like the idea of having multiple 2TB arrays in one machine (or, more to the point, all connected to the same power supply), and that's what it would take to get similar storage densities.
Besides, it's not like I have clothes to put in my closets.