I don't know if setting up a RAID array for this sort of thing is nessicary.
How much do you want to spend protecting information that you download from the internet in the first place?
Your going to be more then doubling your cost per gig of storage. You have to have a extra controller card and two drives for raid one, so thats 100+100+50=250 for the same amount of storage you get from a 100 dollar drive. For RAID 5 you have to get 3 disks, but you get the capacity of 2 disks and increase in performance. However the controller cards that can do RAID 5 properly are more expensive, then regular consumer-grade RAID cards.
RAID 0 is the one that does it for performance only. You take 2 drives and stripe the data accross both of them, the thing is that if you loose one drive you loose the data on both drives.
Anyways any performance benifit is going to be lossed because the network, even 200Mb/s running full duplex 100mb/s thru a switch is going to be slower then a single drive buy itself. (regular 7200rpm drive gives you 45MB/s or so of sustained data speeds with DMA/ATA133 stuff properly setup. 200Mb/s = 25MB/s)
Why not get a DVD drive? You get 4.7 gigs per disk, probably much more if you run aggressive compression. Even at 4.7gigs uncompressed you can get 470gigs of long-term non-volitile storage for around 70 bucks.
Think about this: You get the cheapest CPU you can get, put it in a decent no-frills motherboard. Any past 1gig is plenty. Get 3 of those 200GB drives and a DVD burner. Install a very basic installation of Fedora Linux or Debian or Slackware linux. Give the storage partitions a high quality and fast journalling filesystem like XFS. And then slap a high-quality UPS on it.
You can run a con script to update (for security patches and such) your OS every other thrusday night at 4am (for example) and then occasionally manually backup your newly downloaded stuff to DVDs and stick them in a shoebox.
With a decent router/firewall for network security you can get basicly a extra network based 600gig drive that will be virus and worm immune, your files will be immune from power outages and crashes that occure on your Desktop. And in the event that somebody decides that it would be a good idea to play drunk master kungfu artist and drop-kick your server, then you have the entire thing stored safely away in a box in your closet.
All that for right around 700 bucks. A raid setup with the same storage capacity is only going to much more expensive with very little performance benifit.
I mean it's not like the information stored on the server is of any real critical importance is it, if it's just downloads and stuff? Anything realy important you backup to CD or DVD immediately.
