Instead of using an external hard drive to store a copy of my data on-site, I opted for Network Attached Storage (NAS). There were a few reasons for this, but mainly because I could use high-capacity hard drives set up with RAID to make data loss even less likely.
Also, this particular NAS allows me to stream digital content to my TV. In other words, I can easily back up lots of data and have a personal Netflix service that only has movies and shows I want to watch.