sync two external drives

Hi! I was wondering how to make the contents of two external drives identical, I want to make an exact copy of my 1 terabyte external drive (A) on another 1 terabyte drive (B) because it would be a disaster if I lost the data in case one of the drives breaks down.

It would be great that when I put new files on drive A they also went to the drive B automatically. Same if I erase a file from drive A. This is called syncing isn't it?

I hope you'll be able to help me, this forum has always been so great!! It would also be great if the solution you find was free.

Good question. I'm looking to do the same thing (software RAID) with my .mp4 videos, iTunes, etc...

Its simple, its called RAID, more specifically RAID 1 (mirrored)

RAID - Wikipedia, the free encyclopedia

A Raid set of disks can be set up with disk utility, but you will probably need to beg or borrow a third disk to back-up your data before you create the 1 terabyte (2 x 1 TB drives) raid set

isn't there a way using Automator instead? There is an action called Sync Folders, (how) can I use it?

You could use chronosync or RsyncX do do the job, but it will not be nearly as automatic as a Raid set-up. You just dont want to sync the drives, you seem to want to mirror them.

If you want a GUI for the Unix syncing services then RsyncX maybe what you are after