A 3-2-1 backup strategy is a method for ensuring that your data is adequately duplicated and reliably recoverable. In this strategy, three copies of your data are created on at least two different storage media and at least one copy is stored remotely:
Three copies of data—your three copies include your original data and two duplicates. This ensures that a lost backup or corrupted media do not affect recoverability.
Two different storage types—reduces the risk of failures related to a specific medium by using two different technologies. Common choices include internal and external hard drives, removable media, or cloud storage.
One copy off-site—eliminates the risk associated with a single point of failure. Offsite duplicates are needed for robust disaster and data backup recovery strategies and can allow for failover during local outages.
This strategy is considered a best practice by most information security experts and government authorities. It protects against both accidents and malicious threats, such as ransomware, and ensures reliable data backup and restoration.