I prefer dat areplication to relying on RAID arrays. IE, use your server for backing up important data that is on your desktop.
BUT leave a copy on both machines, this ensures that should one PC or the other fail you still have your DATA.
OBviously for ripped DVD/BDroms this is not a big deal you can always rerip them... and also I really wouldnt want to replicate Terabytes of storage on my network lol . But a 100GB of home movies and family photos gets 2-3 copies on my network. With external storage solutions being so cheap, getting a TB or 2TB drive to put data on then have it sit on a shelf somewhere unpowered is not a bad idea either, just refresh it once in a while.
In fact if it is a small enough amount of data backing up to a solid state solution is an excellent idea as NAND flash (be it a solid state drive or even an Secure digital card) is expected to be immensely longer than magnetic storage. Although no one really knows yet as it is a newer format.
Magnetic storage has been used for well over a hundred years, so its a more known entity.