If you are using the backup module on Magnolia 5.7.x - you must use Magnolia backup module version 2.3 or higher
The Backup module was completely refactored and streamlined in version 2.1. Backups taken with module version 1.6 and earlier cannot be restored with the new one. The module now uses Apache's RepositoryCopier API which is independent of the underlying data storage. The new implementation respects the file store threshold
