Used space gets smaller when copied

Discussion in 'macOS' started by ehatl, Feb 14, 2008.

  1. ehatl macrumors newbie

    Feb 14, 2008
    I have a 2 bay firewire 800 external drive enclosure. I did the following:

    - copied drive A (105gb of files) to drive B
    - drive B now has 83gb of used space
    - compared drive A to B using info on each folder and each folder has the same number of files and are the same size
    - formatted a new drive C
    - copied drive B to drive C
    - drive C has 72gb of used space

    new to the mac but 10 gb copied on the pc is 100gb copied.

    Mac pro
    OS X 10.5.1

    what is going on?

  2. hodgjy macrumors 6502

    Apr 15, 2005
    Drag and drop copying will not copy hidden files. Mac OS X is littered with hidden files. This is why it's important to use cloning software (and bit-for-bit cloners like SuperDuper!).


    There's more to a file size than just the information it holds. Different file sizes use different cluster sizes when making files. So, for example, (and this is just an example and not meant to be absolute truth), if your HFS drive is set at x bytes per cluster and your NTFS drive is y bytes per cluster, the same Word document might be 1 mb on HFS and 1.3 mb on NTFS.
  3. ehatl thread starter macrumors newbie

    Feb 14, 2008
    Disk Utility slows drive B (82gb 6095 files) and drive C (73.7gb 5005 files).
    The actual files count is 5047 and that was from the compare I wrote down from info for drive A and B. I did not look at drive A using disk utility and A was re-formatted to make C so I can't now.


    all drives are formatted Mac OS Extended (Journaled)

    Does SuperDuper work on OS X?

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