While I am thinking about enterprise storage solutions, I should point out an interesting product that Jim McDade told me about a couple of years ago. Jim told me about FreeNAS, a 32MB NAS (network attached storage) operating system that can run from a USB key.
Apparently, if you need a bunch of storage and you don't want to shell out for a commercial NAS product, you could get an old computer, stock it with as many HDDs as you can fit in it and run FreeNAS from one of the disks or from a flash memory device. It supports RAID 0, 1, and 5. A PHP-based web interface is also available.
Anyway, I haven't had the chance to play with this yet, but if you are looking for a homegrown storage solution, this may be worth a try.