Backup Your Content and Custom App Logic in a WordPress Instance

Not all the data in a WordPress instance needs to be backed up since it is part of the core install and can be re-downloaded at any time.

The two types of data that you should be concerned with backing up are the actual content of the site as well as the custom logic that you add to WordPress. All the custom logic lives in the wp-content folder, the only part of the file system that needs backing up.