Why is it necessary to backup the data directory?

Server
1

In the instructions for backing up an owncloud installation here:
https://doc.owncloud.org/server/latest/admin_manual/maintenance/backup.html
it says that you should backup your data directory.

I'm curious why it would be necessary to backup the data directory? I can understand why you would want to backup the config folder and the database but why is it necessary to backup the data directory? Are there files in the data directory that get modified during upgrade?

2

Because you do need to have a fitting set of data between database, config and storage. Must be done at the same time for a secure restore. If you have encryption the keys are also in the data directory and might be affected. Please be assured that we recommend whats most convenient and most reliable and secure at the same time.