Mac - External hard drive backups
Have you tried Xupport?


  Xupport is a multipurpose system utility for Mac OS X. It provides many features to configure hidden Mac OS X and Unix options, to increase system security and performance, to maintain and backup Mac OS X, and to dig deeper into the world of Unix. Xupport 3 is fully compatible with Mac OS X 10.4 (Tiger), 10.5 (Leopard) and 10.6 (Snow Leopard), and is available as Universal Application for PowerPC and Intel Macs. 


Available here