Sorry, n00b here, a little confused by this Q/A in Apple's Fusion Drive FAQ: Can external USB, FireWire, or Thunderbolt hard drives be added to Fusion Drive? External drives cannot be added to Fusion Drive. That means specifically that you can't augment, say, a 1TB Fusion drive to a7TB Fusion drive just by plugging in a 6TB external hard drive, right? I can still use my external hard drives to store media etc? Sorry, I know this is a bit of a facepalm question, but I don't want to order the wrong thing.