I think the reason for the unanswered questions is that, obviously, backup is a vital function and our backup expert and Knight in shining armour, Eloy, is so much in demand.
Assuming you've checked MoodleDocs Backup FAQ, please try an advanced search. If you are still unable to find the answer, please provide full details of your problem. Also, please use a meaningful subject line so that people with similar problems can later find your post.