Hi, I have a question about external hard drives and backing up. I plan to have a lot of photos and videos on my new Mac, which I think will quickly exceed the 200GB internal hard drive on my MBP. So I'm thinking of a 1 TB external hard drive as the primary source of storing these photos and videos. But I'm also looking to back up that external hard drive. So is it just a matter of plugging in a second external hard drive (1.5 TB?) into my MBP every week and Time Machine will know to backup both my MBP's internal hard drive as well as the external hard drive? Or is it more complicated than that?