There was a time when all my media (TV shows, music, movies) fit on a single 80GB hard drive, but now that broadband speeds have more then doubled since those years I’ve gotten a lot more media and filled many more hard drives. Currently I have about 1.4 terabytes spread out across 9 external hard drives. They’re all connected to my MacMini using Firewire and USB. I use iTunes to manage all of the media. A couple weeks ago a customer came in and was surprised to learn that it’s possible to use multiple hard drives with media on them in iTunes. Some people think it’s possible only to keep your media in your Music folder or on a single external hard drive. This is untrue.
If you get to the point where your media spans across multiple hard drives (internal or external) you can still get it to all show in a single iTunes library.
If you open iTunes and go into the Preferences and look under the ‘Advanced’ tab you’ll see the option to choose where your iTunes library is kept. I keep mine on one of my external drives. If you don’t plan on purchasing any movies or music or downloading podcasts I would say leave it as default, if you do, I would move the location to your external hard drive. From time to time it’s a good idea to back up your iTunes folder.
Now that we have a location for our iTunes library we can start adding media to iTunes. Information about where each music, movie and TV show file location is recorded into a special iTunes library file (iTunes Music Library.xml). So no matter where you file is, this special library file will tell iTunes where to look for it. Of course you must have the hard drive connected or it’ll fail to find the file. Once you’ve added all the media from one hard, just move to the next. I use the ‘drag n’ drop’ method, but you can also go to File >> Add To Library, from iTunes.