This whole Manual describes how to recover lost data. This chapter describes how never to get there. It's not a commercial paradox: a serious lab prefers a client who doesn't need it. Recovery is a safety net, not a backup strategy.
1 · The 3-2-1-1-0 rule
The historic 3-2-1 rule has evolved to address ransomware and silent errors. The modern version, 3-2-1-1-0, reads as follows:
- 3 — keep at least three copies of your data (the original + two backups).
- 2 — on two different media types (for example internal disk + external disk, or NAS + cloud).
- 1 — with one copy off-site, geographically separate (cloud, vault, another building) to survive theft, fire or water damage.
- 1 — with one copy offline (air gap), physically disconnected from the network.
- 0 — zero errors: backups are verified and restores are tested.
2 · The air gap, ransomware rampart
The fourth pillar — the offline copy — has become decisive. Ransomware spreads to everything reachable from the network: workstations, servers, NAS, even connected backups. A copy kept physically disconnected (unplugged disk, tape, immutable cloud) escapes encryption because, at the moment of attack, it's out of reach. It's often the only copy that survives — and the one that avoids paying a ransom.
3 · RPO & RTO: measuring your risk
Two indicators frame a strategy, especially in business:
- RPO (Recovery Point Objective) — the amount of data you accept losing, measured by the age of the last backup. Daily backup = 24h RPO; continuous backup = a few minutes' RPO.
- RTO (Recovery Time Objective) — the acceptable time to get the service running again after an incident.
Defining your RPO and RTO turns backup from a vague intention into a quantified requirement, sized to the real criticality of the data.
4 · The "0": testing your restores
This is the most widespread mistake: believing you're backed up without verifying it. A backup that won't restore isn't a backup. The "0" in 3-2-1-1-0 imposes two disciplines: verifying the integrity of backups (checksums, Bit Rot detection) and regularly testing a full restore, on separate hardware. A quarterly test reveals corrupt, incomplete or undecryptable backups before it's too late.
5 · In practice, by profile
Individual — an external disk + a personal cloud often suffice to reach 3-2-1; unplugging the disk between backups adds the air gap. Check once a year that your photos open.
Freelancer / small business — add an off-site copy and a rotation of disconnected media. Document where your encryption keys are.
Enterprise — formalize RPO/RTO by data type, include an immutable or offline copy, and write restore testing into the business continuity plan.