What is time machine actually backing up?

Discussion in 'Mac Apps and Mac App Store' started by tivoboy, Mar 25, 2009.

  1. tivoboy macrumors 68040

    May 15, 2005
    So, I tried a search for this but didn't really find any details or threads.

    I did a nice TM backup on a new MBP, came to about 40GB total, I excluded folders like my itunes library and desktop, where I store a bunch of installers and such.

    after a week, I did it again, and it added about 1GB.

    Then, after another week, just internet use, a BIT of email and such, I did another backup and it added 8GB to the total, to a total now of 49GB?

    WHAT THE HECK was in the newest 8GB? Is that another new snapshot or something, since I CERTAINLY didn't add 8GB of stuff?

    I cannot imagine why it would increase so much, is this type of thing normal? Will it simply add this much every couple of weeks, if so I am going to need a bigger boat!
  2. dvdhsu macrumors 6502a


    Mar 28, 2008
    Palo Alto, CA
    I'm not sure what Time Machine has been backing up, but it really shouldn't be backing up that much.
    Sorry I can't offer any more help.
  3. killmoms macrumors 68040


    Jun 23, 2003
    Washington, DC
    You might not've added 8GB of stuff, but you might've changed 8GB of stuff. Have any particularly large files that get altered regularly (Entourage e-mail database, Aperture database, virtual machines from something like vmWare or Parallels, etc.)? Those are the usual culprits.
  4. tivoboy thread starter macrumors 68040

    May 15, 2005

    Yeah, this just seems to be getting worse, not better.

    For example, my HD is 50GB used, I had a 51GB TM backup, today after about three weeks I ran the update again. I even excluded things like itunes and movies, which I don't really have much in.

    I have been using MAIL and internet, but keep caches clean and such, nothing else, Haven't added anything really to the computer.

    And, the TM did ANOTHER 25GB ADD to the TM backup, which is now 76GB large?

    What CAN that possibly be, it seems more like a complete drive backup EVERYTIME?
  5. Signal-11 macrumors 65816


    Mar 23, 2008
    2nd Star to the Right
    Are you running Parallels, Fusion or any other VMs that essentially run from a disk image?
  6. tivoboy thread starter macrumors 68040

    May 15, 2005
    I do

    I do have a VM ware xp setup in there, it was setup about six months ago, hasn't been used since then. It shows 17GB in the library, but hasn't changed over time.

    But, if the MAC HD shows just incremental growth in usage from 50GB to 51GB in the past month, why would the TM backup interpret anything as so much more?
  7. Signal-11 macrumors 65816


    Mar 23, 2008
    2nd Star to the Right
    You can change as little as 1 bit in a 10GB file and TM will back that up as a inc change.

    Assuming that things are working the way they should and this isn't a legit bug, which it's probably not, you have some large files that are being changed. Maybe not enough for you to notice, but definitely enough for TM to interpret as a change.

    Are you sure your VM hasn't been accessed or changed in any way? Others on this thread have mentioned the other obvious culprits but you should think about other things you could have done - ie, video files, certain Mac games that run in Cider wrappers, blah blah blah.
  8. tivoboy thread starter macrumors 68040

    May 15, 2005

    wow, so what you're saying is, that if I have a 15GB VM, and open it, and close it for example, it will indeed have changed, and then the TM backup will see that as a CHANGE and rebackup the entire 15GB VM?

    That sounds pretty beat, and WAY inefficient.
  9. Signal-11 macrumors 65816


    Mar 23, 2008
    2nd Star to the Right
    The computer doesn't know that's dumb or not the way you want to do things. Depending on your usage patterns, that could be exactly what you want.

    But yeah, it's pretty inefficient for the average, day to day user. The computer follows the rules, so what you need to do is make a rule NOT to do this. Just add the VM to your exceptions list. See if that helps.
  10. GimmeSlack12 macrumors 603


    Apr 29, 2005
    San Francisco
    This is a pretty good approach to what is being backed up and/or how it works. I don't have dramatic backups like the OP is saying, but then again, I really don't care because I know Time Machine works. It's saved me from hard drive failures twice.

    EDIT: I recommend using TimeMachineEditor for scheduling your TM backups (instead of every 10 minutes).
  11. themoonisdown09 macrumors 601


    Nov 19, 2007
    Georgia, USA
    Back when I used Parallels, that's what I did. I didn't want my VM to backup every time I used it.
  12. tivoboy thread starter macrumors 68040

    May 15, 2005
    drop it

    Is there a way to drop the HISTORICAL TM backups of the VM out of the backup store?
  13. mrkgoo macrumors 65816

    Aug 18, 2005
    You can enter Time Machine, then click on a file - click actions - remove all backups. This remove all incidents of that file from Time Machine. On your next back up, it will start again with that file, unless you have made it an exception.
  14. Dunmail macrumors regular

    Mar 27, 2009
    Skipton, UK
    Backup systems usually work on file timestamps. Don't know if TM does but it's quick enough doing the hourly backups that I'm fairly sure this is the case. TM will have a list of all the latest timestamps for each file, it then compares the current timestamp for a file with that in its list. If the file has a newer timestamp then the file is seen as changed so it is added to the backup.

    The alternative is to run some sort of checksum over each file. Even with modern machines that is likely to take considerable time for several tens of Gigabytes of files.

    Two tests you can do:

    1. Open the terminal and find a plain text file in your Documents folder hierarchy. Lets assume it's called test.txt

    Type the following:

    touch test.txt

    And press enter/return. This sets the timestamp of the file to the current time.

    Now when TM runs, test.txt will be added to the latest backup.

    2. Now make some modifications to test.txt and type the following:

    touch -t 200805071000 test.txt

    and press return. This sets the timestamp for the file to 10am 7th May 2008.

    The next time TM runs test.txt should not be added to the backup even though it has changed as its timestamp will be older than that in the list that TM is using.
  15. Macup17 macrumors newbie

    Mar 18, 2009
    Montreal, Canada
    I just started Time Machine yesterday and I have Fusion. I did remember today having read on the forums to remove VM from backing up. How do you do that? I went into preferences and added Fusion(the application) to exclusions. Is that right?
  16. tivoboy thread starter macrumors 68040

    May 15, 2005

    Where I added it, was actually in MY DOCUMENTS folder, and there is a VM folder in there. I added that to the exclusion list in TM.

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