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Difference in sizes of copied Aplibraries

358 Views 6 Replies Latest reply: Jul 12, 2013 6:55 AM by Victoria Herring RSS
Victoria Herring Level 2 Level 2 (290 points)
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Jul 10, 2013 5:04 PM

I am backing up/copying over some Aplibraries onto external drives and find that copy 1 might be 25.04G in size but the same Aplibrary, same date and time of creation is 25.13 in size.  Should I worry about this???  The larger size appears to be on the start up drive [Pictures folder] and the external drive has the 'smaller' one.

Mac Pro, Mac OS X (10.7.5), 17G RAM
  • Thomas Emmerich Level 4 Level 4 (3,470 points)
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    Jul 10, 2013 7:04 PM (in response to Victoria Herring)

    It could be due to comparing "Size on disk" instead of filesize. The filesize is the exact number of bytes needed whereas size on disk is how much space of a disk drive is required. The descrepancy arrises when you have two disk drives with different sector sizes.


    (example: a 513 byte file on a disk with a 512 byte sector would require two sectors and take up 1024 bytes on disk. That same file on a 4096 byte sector would take up the entire 4096 bytes on disk. It doesn't seem like much difference but if you have thousands of files, they add up.)


    Use the Get Info command in the Finder for each copy of the library and you'll see the size of the library and also the size on disk.


    If you're looking at the size in a Finder window I believe it is showing "size on disk".


    This is only a theory. See if it helps.

  • léonie Level 8 Level 8 (46,560 points)
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    Jul 10, 2013 10:05 PM (in response to Victoria Herring)


    does your external drive have the same file system? Is it formatted "MacOS X Extended (Journaled)"?

    If not, I'd reformat the drive, before you copy the the library there. An Aperture library will not work properly on a drive not formatted for mac.


    You'll see the formatting in the Info panel of the drive when you select the drive in the Finder and use the command "File > Get Info".



    Screen Shot 2013-07-11 at 07.03.21MESZ.PNG

  • Kirby Krieger Level 6 Level 6 (11,570 points)
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    Jul 11, 2013 3:14 PM (in response to Victoria Herring)

    Guessing -- -- I suspect the difference has to do with how OS X copies Finder packages.  The Library is a Finder Package.  Finder Packages are collections of Finder Folders and Files which show in Finder as a single file.


    What happens if you copy your Library from one drive to another drive, and then copy it back?  Is there any reported change in size between the original and the "copied-over-and-back" one?


    In the past one could force a stringent defragmentation of the Finder Package by copying to a different drive (the OS copied by file and rearranged the sectors).


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