Years ago I used to keep my files saved in an external hard drive; every picture I had taken, photos of my travels across Europe, my wild college days, and so on. I also kept my entire iTunes music library stored on the same external hard drive. Sadly, one day the hard drive just stopped working. Lesson learned: always keep a backup of your backup. Thanks to the advent of cloud computing, these days you don't really have to worry about losing copies of things when a single device you own breaks down.