Instead of spending your next month or year re-inventing the wheel, adopt an open source backup solution that has had top level programmers working on it for many years.
If I were in your situation, I would adopt Amanda. It will manage all that for you using native tools on your SLES servers, managing the tapes in your library, and staging all the backups for efficiency. You can find a number of links to it here http://www.linuxquestions.org/bookmarks/tags/backup
. There is a quickstart guide on the amanda wiki under user documentation -- http://wiki.zmanda.com