A 3-2-1 strategy means having at least three total copies of your data, two of which are local but on different mediums (read: devices), and at least one copy off-site. //

There is no such thing as a perfect backup system, but the 3-2-1 approach is a great start for the majority of people and businesses. Even the United States government recommends this approach. In a 2012 paper for US-CERT (United States Computer Emergency Readiness Team), Carnegie Mellon recommended the 3-2-1 method in their publication titled: Data Backup Options.