The 3-2-1 backup rule recommends three copies of data across two types of storage, with one copy kept away from the primary location.
For implementation, distinguish a backup from synced storage: depending on the service and settings, deleting a local file may also delete its online copy.
What does the 3-2-1 rule mean?
Keep three copies of your files on two different storage media. These days, two different media often means two different devices. Put one copy in a different location than the others. That way, if a fire, flood, or burglary hits your primary storage, you can still have a copy somewhere else.
Photographer Peter Krogh popularized the rule in his book “The DAM Book: Digital Asset Management for Photographers,” released in 2009. The idea is to not rely on a single copy or a single location.
For example, you can have your files on your laptop, on an external drive, and on a private online storage space. Ideally, the copy outside the home is far enough away that it won't be affected by the same event that hits your home.
What to look out for in online storage
Services like iCloud and Google Cloud can be used to store files. However, depending on the service and your sync settings, deleting a file from your computer may also delete it from the online space.
There are also services that automatically create full copies of devices. They vary in the amount of space available and their prices. Even a copy in another location can be affected by a file-locking attack if the device is connected to the network.
File protection needs vary from person to person. An individual does not need to follow the same solution as a multinational corporation. The 3-2-1 rule provides a framework for having more than one copy and not all in the same place.
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