Time Machine & Backup Size

Discussion in 'Mac Basics and Help' started by krawfo, Mar 5, 2014.

  1. krawfo macrumors regular

    May 4, 2011
    I'm backing up a 1TB drive that has 532GB of data on it. I formatted a 1TB drive and configured Time Machine to exclude Apps, Caches, System Files, etc. Estimated full backup size is 331GB. Twenty one days later my backup drive is full.
    Obviously, I'm missing something. I can't figure out why 532GB of data has filled a 1TB drive.
    Any insight would be appreciated.
  2. Murdocke macrumors newbie


    Mar 5, 2014
    Birmingham, England
    Have you tried loading the drive and deleting the backup file on it (including emptying the trash) and starting a fresh?
  3. krawfo thread starter macrumors regular

    May 4, 2011
    Thanks for the reply. Pardon my ignorance, but what do you mean by "loading the drive".
  4. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    Time Machine (TM) keeps versions of files, so for example, if you have a 2GB video that is backed up to TM and you edit that video... the whole 2GB video gets backed up again taking another 2GB of space on the TM disk.

    Another example.... you download a 3GB video and watch the video, then delete it. If TM happened to do its hourly run during the time that video was on your system, that is another 3GB on the TM disk.

    The same thing happens with any documents or anything else you edit. All these versions get saved to TM. Over time that can add up.

    Just a suggestion. You don't need to exclude caches etc fem TM backup as those are excluded by default. I would just let TM backup everything so it could be used as intended for a full restore id disaster strikes.
  5. snberk103 macrumors 603

    Oct 22, 2007
    An Island in the Salish Sea
    TM is working as designed. This is because TM is not a simple backup, but a versioning back up solution. It is designed to allow you to go back and retrieve documents that you may have deleted, or to retrieve earlier versions of a documents that you may have overwritten. Since these different versions need to be stored, a TM disk will fill up. When a disk becomes full, TM will delete the oldest versions to make room for the new. The bigger the TM disk, the older the documents that TM will be able to save for you. What Weaselboy wrote is correct...

    In my case I use a cloned backup (runs automatically at night) to make a bootable backup of my system. I'd use this to recover from catastrophic hardware failure. I also use TM - which I use to recover from user errors. That is... to recover files I've deleted or overwritten when I shouldn't have. My cloned backup is also cycled to a safe off-site location.

    Hope this helps.
  6. Tumbleweed666 macrumors 68000


    Mar 20, 2009
    Near London, UK.
    Chances are you'll be frequently altering one or a small number of very large files.
  7. krawfo thread starter macrumors regular

    May 4, 2011
    Thanks everyone. That makes sense. Mystery solved.

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