Backup

A backup is a secondary copy of data — files, databases or entire systems — created so that information can be restored after hardware failure, ransomware, software bugs or plain human error. It is the last line of defense when every other safeguard has failed, and the foundation of any business continuity plan: redundancy keeps a service running, but only a backup lets you travel back to the state before an incident.

How backups work

Three basic strategies are combined in practice: a full backup copies everything, an incremental backup stores only changes since the last copy of any kind, and a differential backup captures changes since the last full one. These are arranged into schedules with defined retention, for example daily incrementals plus a weekly full copy kept for a month. The widely recommended 3-2-1 rule calls for three copies of your data, on two different media, with one stored off-site. A backup should not be confused with a snapshot, which freezes system state on the same storage array — fast to create, but useless if the whole server burns down. Against ransomware, an immutable backup adds a write-once guarantee: nothing can overwrite or delete the copy before its retention period expires.

Practical applications

Two metrics shape every backup strategy: RTO and RPO — how quickly the system must be back online and how much data you can afford to lose. Just as important as making copies is regularly restoring them: an untested backup is a hope, not a plan. Hosting and VPS providers such as Nodea run automated account backups on a schedule, but for critical workloads it is wise to keep an additional, independent copy outside the provider's infrastructure. Popular tooling includes rsync, restic, BorgBackup and database dumps driven by cron jobs.