What in the world is it copying?
 

I have notice that when I back up, SD tells me it is copying 4 and 5 Gigs. I know I have not downloaded that much or created that much content. So, I decided to try this: I did a regular back up as usual -- and again, it told me it was backing up an amazing amount of stuff, like 4 Gigs-- . When it finished, I went immediately and did another back up without changing anything in SD or my computer. To my amazement, SD copied another 800 Mb!!

Where is all that stuff coming from?
Does any body know what's going on?

If this is your startup drive, things are changing all the time... you're never going to get two runs back to back that are identical...