So you keep a set of HDs in a separate physical location and rotate drives for fire safety?
(Used to that in the olden days when the only affordable way to back up was on video tape. A,B,C copies. Always one in the second locale.)
My primary file server is a smallish Win2K box with a 300GB RAID5 array, I have a secondary 700GB RAID5 NAS, and then a USB2 removable drive enclosure with a collection of 250GB single drives that can go off-site.