Backup and migration
Backup and migration belong together: technically a migration is nothing other than a backup on the old machine and its restore on the new one. The delivery package includes the necessary aids for both.
What gets backed up
Section titled “What gets backed up”A backup has to cover the entire state of an instance, and only the state. That includes the database with the content of the instance, the uploaded files and the configuration together with its secrets. The secrets are indispensable: without them part of the database stays unreadable even after a complete restore.
What can be derived again from this state does not have to be backed up. Such derived data rebuilds itself after a restore. Runtime logs are not state either.
Backing up regularly
Section titled “Backing up regularly”The backup is set up once and then runs on a schedule, with a retention rule that lets old states expire after a defined period. How often you back up follows from a single question: how much work may be lost in the worst case?
Restore and its effect
Section titled “Restore and its effect”A restore is destructive. It replaces the current state of the instance with the state from the backup; whatever has been created since is gone afterwards. The path there therefore requires an explicit confirmation. Treat a restore as a deliberate intervention, not as a routine move.
Migration to a new server
Section titled “Migration to a new server”A migration leads through a backup of the old instance, the setup of the new machine and the restore of that state. Three points decide whether it succeeds:
- The secrets of the existing instance are carried over and not regenerated.
- The new instance is checked before the switch-over, not afterwards.
- Between the decisive backup and the switch-over no further work may happen, otherwise exactly that work is missing on the new server.
The copy of the backup transported for the migration contains secrets and customer content. Delete it after the migration; only the regular backup remains.
Two recommendations that really count
Section titled “Two recommendations that really count”- Test the restore once before you rely on it. A backup that has never been restored is an assumption, not a backup. The test belongs on a test machine, not on the production system.
- Mirror the backup off the server. A copy on the same machine protects against accidental deletion, not against the loss of the machine. Because a backup contains secrets, it belongs in a cloud only encrypted, and never in a repository.