Well, I am a HUGE rsync fan, it's fast, free and works great, whether connected to a local drive or over a network (local or Internet). Plus, it's already installed on your Mac. The only thing you need to be concerned with is if you want that drive to be bootable, you need to take steps to make it bootable once your 'rsync' is done.
For whatever reason, about a year ago, I decided to go with SuperDuper for making backups and it works good. It provides some of the facilities of rsync but is also more limited than rsync, but does take care of making your drives bootable once the backup is complete.
Rsync is as easy as opening terminal and let's say your external backup drive is called "Backup" and your internal drive is "MacintoshHD", then you could simply do a:
Code:
rsync -av /Volumes/MacintoshHD/ /Volumes/Backup
If you have older applications or files that use resource forks, then you will want to add a "E" to the option set, but can cause unnecessary re-copying for files unchanged. Once a full backup is made, it only takes about 18 minutes (or less) run "sync" your backups later, and this is based on about 300GB of data. Have a script run overnight (if the system is on all the time) or just run it when you want.
If you are running backup from a MacBook to a local iMac on a network, such as at home, you can run it over SSH...
Code:
rsync -avz /Volumes/MacintoshHD/ -e ssh user@192.168.0.101:/Volumes/Backup/Macbook
VERY SIMPLE STUFF.
One note though, if you do try rysnc above and it works like you want, then add the flag "--delete" to the line as well, this will delete anything on the remote drive that is not on the local. But I don't put that on there since I'd rather not have you goof up and delete something locally if you turn your paths around in the syntax. You can also leave off the "v" if you don't want it to be verbose, which if running via a script overnight would not be necessary, but when running the first few times or manually, it might be nice to visually see what it is doing and which files it is updating.