I used my MBP back-up on my external drive to set up the MBA. Today I thought to back up the MBA using Time Machine since it's been a month. I decided to do as a separate (new) back-up to keep the two machines distinct. However, in the last 3 plus hours, it has only backed up 17.71 GB out of 322 GB. Given how FAST the time machine worked when I did the initial migration (under an hour), what may be going on here? I'm thinking of just canceling the process, but have no idea what the glitch is.