I just purchased a 3 TB Airport Time Capsule to run time machine on. I used to send the backups to my drobo, but was running low on space there and wanted to upgrade to 802.11 AC as I have a new rMBP and this would kill two birds with one stone. Got the Airport up and running and am in the updating process. My rMBP has the 1 TB drive of which 188 gigs are free. My Time Machine backup is estimated at 2.12 TB? WTF? not sure where the other 1.3 TB are coming from? I have attached drives to the rMBP but in the Time Machine preferences I made sure they weren't included. What gives? I was hoping to use this drive to store extra data (GoPro files etc) but at this rate, it will be full in a week!!!