So basically this is what I would like to know...

Say I have an external hard drive that I save large movie files and other data onto so its doesn't take up space on my internal hard drive. Is there a way I can use a second external hard drive to backup both my first external and my internal hard drive? If so, is there different ways of doing it, say my first external is RAID and I have movies on one part and I backup my internal on the other part and then backup just the movies on the second external? If anybody has experience with this I would appreciate your help!