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  1. #1

    weatherreport's Avatar
    Member Since
    Apr 05, 2010
    Problem with copyin large sized folders... File sizes changed after copying...
    Hi everyone,

    I'm back with another strange question.

    I am reorganizing my external drives. Copying all of my stuff from one USB external disk to another... So that i can format them both in HSF...
    Yesterday I copied 1 TB of data stored in a fat32 hard disc to a freshly formatted mac journaled disc.
    I wanted to check if everything is ok... And looked at the size of one particular folder on both on the original and the copied disks. But their size don't match...
    For example one folder (80gb on the source disk) appears as 79.8 gb in the destination disk. Folder and file numbers also don't match exactly...
    What do you think? Is this normal?
    BTW I am copying them on macbook pro.

    Thanks already for all your replies...


  2. #2

    Raz0rEdge's Avatar
    Member Since
    Jul 17, 2009
    27" i7 iMac, 15" Macbook Pro TB, 13" Macbook Air, iPhone 6S, iPod Nano 7th Gen
    Transferring files from one filesystem to different type and drives of different sizes will result in different representations of file sizes..Also if you are running Snow Leopard on your Mac, they've changed to start reporting 1 MB as 1,000,000 bytes as opposed to 1,048,576 bytes..

    The way to confirm that the files are the same are to use something called SHA1 checksum. What you should do is generate the SHA1 checksum of the original on the FAT32, and then do the same on the copy on the Mac directory.

    Mac OS X: How to Verify a SHA-1 Digest

    The link above will show you how to generate the SHA1, once you do this, what you should see is the EXACT same checksum for both files. If so, they are identical down to the bits..


  3. #3

    weatherreport's Avatar
    Member Since
    Apr 05, 2010
    in pulses
    Hi Raz0redge,

    Thanks for the post.
    I had no idea about checksum and your suggestion really worked out well.
    It will surelye be a useful tool from now on.

    Thanks again.


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