the 3-2-1 backup rule
expressionops cultureIT support
The backup rule of thumb: three copies of the data, on two different media, with one copy off-site.
Simple enough to remember mid-disaster, and it survives most single failures: device death, site loss, even ransomware if the off-site copy is offline or immutable. The modern extension is 3-2-1-1-0: one copy offline, zero restore errors.
Also known as: 3-2-1 rule, 3-2-1-1-0