I know the feeling of just wanting your data to be safe. I really don't want to have to re-rip all those CDs, let alone the impossibility of retaking ten thousand photos!
I have my RAID set up as a local disk on my G5. In other words, I don't have a server at all. The RAID volumes just show up on my desktop as local drives. They never have to spin up, they are just always there.
One interesting note about RAID. A RAID is actually less RELIABLE than a normal disk.
If you take 14 hard drives (ignore the controller for now), each with a Mean Time Between Failure of 500,000 hours each and tie them all together. You get a system with a MTBF of only 35,714 hours! A decrease in reliability of 93%. What makes RAID 5 (with distributed parity information) so great is that it is FAULT TOLERANT.
In theory anyway, my RAID can have 4 drives, one controller, one power supply, one cooling fan, and one UPS all fail all at the same time without losing data. I have a far greater chance of having some failure than just a single disk drive with a MTBF of 500,000 hours. The difference is that when I have a failure, it is likely that it won't be catastrophic.