[2mol]

Great answer, thank you. I agree with your point about testing the restore process, right now I'm trying to think of a way to automate it.

As a side note: for example we had some backups that are probably useless, because they are way too small. Catching this would mean more manual regular checks, or some automated rules, at which point it becomes quickly more complex again.

[parasec]

The backup part is quite easy - generate a well-known file with 1kb of data and include it in your backups. After the backup completed, validate that you can restore the well-known file and compare the content of the original and the restored. Easy to automate if you run a well-customizable backup system.

Storytime: I did not check the restoration of my backups some time ago and had a faulty harddrive, so I needed to restore the backup. Backup was also as dumb as possible - essentially a tar and encrypting it with openssl. So I reinstalled the server, tried to decrypt it - got the error, that the key was wrong. Took me a good weekend to find out, that openssl changed the default hash algorithm between openssl 1.0 and 1.1. This would not have been catched with the proposed system, but now I really pin all default options in my scripts as well.