For better protection, DriveHQ Online Backup doesn't automatically delete files already backed up on server. You can manually remove those files by logging on the backup client software, click on Manage Tasks, select the task and edit it, then click on the button "Delete un-used files on server". DriveHQ Online Backup can also keep multiple versions of your files. So in case of accidental overwrite, you might be able to restore an older version if the older version has been backed up.

Some users use DriveHQ FileManager as a backup tool. It is ok, but you need to manually drag and drop files. FileManager is designed more for sharing and collaboration among a group of people. The Folder Synchronization feature is not as safe as Online Backup: with synchronization, if you delete files locally, it will also delete files on server. So you could lose both files.