RAID?
I have all my important data on a
NetBSD server running two 120GB IDE drives as a mirror.
One could do the same thing with a software RAID 1 on OSX. Of course there's a speed penalty, but my theory is, desktops have fast but relatively volatile RAID 0 stripes (basically as scratch space, since you stand twice the chance of losing everything on a two way stripe) with all critical data living on a mirrored volume, either on the same machine, or on a server (RAID 5 would work great too, but jeez, who can afford that at home?).
With data use and hard drive size growing so fast, this seems the best option, my 34GB of mp3s will barely fit on a DLT (if I'm lucky) and it would take hours and cost big bucks for the drive and media. Add in the rest of my data, and you're talking 12+ DVD-Rs, plus restore time. Hard drives are basically a disposable commodity nowadays, so it seems one has to balance out their poor reliabilty by leveraging their low cost.
...doesn't really work with an iMac on a small desk, though... so I guess I'll say "Hard Drive" and use an external firewire when I'm in that position.
-alex.
[edited to correct usage of "RAID 0" and "RAID 1"]