Right, no arguments here. Backing up is really hard. Many backup systems are "push", and so you have to limit the production system's access so that it can't ma

Right, no arguments here. Backing up is really hard. Many backup systems are "push", and so you have to limit the production system's access so that it can't maliciously overwrite old backups. From what you describe in the last paragraph, that sounds like a special Owncloud client. It needs decryption keys and it needs some automated tests for verifying the backup which vary based on your use case. I've recently been testing git-annex with the webdav special remote, and it mostly solves the integrity piece but a) if you want encryption you lose the web UI, b) even if you don't want encryption, you still lose the web UI because there are no indexes, and c) it would be too high a bar for most people to set up.