If you're going to do Linux backups and you want them to be trustworthy, you should really read the following article on reliable Linux backups: How to backup Linux, BSD and other Unix-like systems properly

In this article, the author (a good buddy of mine) describes in great length the does and don't of backing up Unix-like systems. He also goes into great detail about the advantages and disadvantages of various backups methods, so that you will be able to estimate whether you're beter of with rdiff-backup/rsync or something like Dar.

Read it. It will almost inevitably make you consider something you've never considered before. It did me.