The 3-2-1 Backup Rule Explained: Why “3”?
When people talk about backup strategy, the “3-2-1 rule” comes up often: three copies of your data, on two different types of media, with one copy stored offsite. It’s a catchy sequence of numbers, but few people stop to unpack what each digit is actually protecting against. This post breaks down where the rule comes from and how it maps onto a real backup implementation. Note: The 3-2-1 rule is widely attributed to photographer Peter Krogh. It isn’t a formal standard set by any single organization — it’s a rule of thumb that spread through practical experience. What each number protects The rule bundles three separate conditions: Number What it …