Here is my setup (well, it will be my setup on Christmas morning!): A. 128GB Air. On that SSD will be music and photos I use frequently. B. Big external HD. On here are ALL my photos, ALL my music, etc. About 350GB. C. Dedicated Time Machine backup drive. Is there a way I can use Time Machine to back up both A. and B.? That is, I want, when I plug in my Time Machine drive, for both the Air and External to be backed up? Does this make sense??