I've been engaged in a bunch of discussion about how to keep your personal data safe at home. I hear a lot of people say they want to build a RAID5 array in a server, and put their family photos on it.
I can think of many ways to lose my data:
While all of them are potentially real, only #1 & #7 are actually likely to affect my data. In my lifetime, I have lost data to #1 & #7, and never to #2-#6.
RAID5 and the like only protect against #1, and even then a dying controller can nuke your data.
Seriously though, my biggest fear is that *I* will delete my data.
The only way I know to protect against all of them is to have an offsite and offline backup. (Even that may not be enough for #5.)
To that end, I keep an external drive at work, disconnected. I update it periodically. Luckily this is simple enough for anyone to do. (You probably need to be selective about what you back up this way, to keep it all on one drive).
Another strategy that complements this one quite well is to provide mutual data duplication with a friend or relative in another part of the world. The further, the safer. Foldershare makes this doable.