Best practice: keep 3 copies of data, on 2 different media types, with 1 copy offsite.
The 3-2-1 backup rule is a proven strategy for data protection: maintain 3 copies of important data, store them on 2 different media types, and keep 1 copy offsite. This protects against single points of failure—hardware failure, theft, fire, or localised disasters. Modern variations include 3-2-1-1-0 (adding 1 air-gapped/immutable copy and 0 errors in backup verification) to address ransomware threats that target connected backups.
Why It Matters
The DSC Perspective:
3-2-1 provides resilience against multiple failure scenarios. Ransomware has added urgency—attackers target backups. Ensure at least one backup copy is isolated from your network.