Time Machine initial backup way too large
See if there are files marked inprogress on the machine's backup folder


TimeMachineDisk -> Backup.db -> MachineName.  

You can try to remove them with tmutil.  Do not remove them with finder.


You can get enormous files if the source disk has has certain classes of file system errors.  Boot off of your recovery partition or off a DVD and run diskutil repair disk.  Then us tmutil to remove the monster backup and try again.
Check out Pondini's page about Time Machine.  http://pondini.org/TM/Home.html  This is an excellent information and troubleshooting guide.


Thanks, BTW for the headsup that an rMBP has no ethernet jack. This makes it a non-starter for me.