Explainer
Backup and restore testing
Taking backups is only half the job; the real question is how quickly, and from which point, data can be brought back when needed. Why the 3-2-1 rule and regular restore tests belong together.
Verimel2 min read
In many organisations, backup runs as a background task that is forgotten after it is set up. The backup software sends a success message every night, and that message is taken as reassurance. Yet the value of a backup only shows when something has to be restored.
The 3-2-1 rule
The widely used 3-2-1 rule offers a simple framework:
- Keep at least three copies of the data (the original and two backups).
- Store the copies on at least two different types of media (for example local storage and the cloud).
- Keep at least one copy in a different location, independent of the main system.
The rule aims to prevent a single failure, fire, theft or ransomware attack from affecting every copy at once. Today, adding a copy that cannot be modified or is kept off the network is also widely recommended.
Two basic questions
Two questions should be answered when setting up a backup plan:
How much data loss is acceptable? A nightly backup means data entered during the day could be lost. For some data that is acceptable; for some it is not.
How quickly must the system be back? Half a day may be enough for a file server; an application that takes orders may need to return much faster.
The answers determine backup frequency, the media used and the cost.
Restore testing
The only way to show that a backup really works is to run restore tests at regular intervals. During a test, check:
- Can a chosen file or folder be restored to a given date?
- Does a server or application work after being fully rebuilt?
- How long did the restore take, and does that meet expectations?
- Are the necessary passwords, licences and documents accessible?
Keep written records of the results. The next test also checks whether the gaps found last time have been closed.
Common gaps
- Assuming that data in cloud applications is automatically backed up by the provider. Many providers keep their infrastructure running but recommend separate backups against user-caused deletions or changes.
- Backups that can be reached with the same privileged account as the main system. A compromised account can then delete the backups too.
- Files on laptops left outside the scope.
Backup is not a product but a process that is tested regularly. When the plan, the tests and the responsibilities are defined together, the reassurance becomes real.
