So you're going to get people who fall into a couple camps on this. Build your own raid server, mirror to another location locally, cloud, etc.
I'm going to throw out what I think is maybe the best security vs. easiness solution (obviously you can build your own box for the best price and hack it to do anything you can dream). My recommendation is getting a Synology NAS. It's pretty much a server that does most everything most people would want at a pretty darn reasonable price and it's dead simple. I bought their $300 two bay system, put a couple drives in it, the drives are automagically set up in a RAID solution that lets me hot-swap either should one die, and perhaps best yet Synology has a one-click install "app store" that takes care of most things you could need. They've a few relatively cheap cloud backup systems built in through a few reputable companies, easy to setup remote access, iOS and Android apps, and you can even use them as a media server. You can also setup automatic backups with both windows and mac machines very easily to the Synology. The list of what they can do out of the box is pretty incredible.
Now Synology units are not as flexible, obviously, as if you built your own box. And not quite as cheap. Your choices will also be somewhat limited in terms of cloud backup providers. But if a drive dies, you just replace it, and at a fraction of the cost of lets say a Drobo. And with all of the functionality you get out of the box you'll be setup with everything you could want, and more, probably the same day it arrives on your doorstep.