size: versus size on disk:

I copied a large directory to a backup drive, preparing to replace the HD on which the directory currently exists.

After copying, the "size" of source and target both match:
7.14 GB (7,673,318,222 bytes). The number of files and folders match as well.

However, the "size on disk" does NOT match.

On the source drive:
7.24 GB (7,783,518,208 bytes)

On the external (target) drive:
8.21 GB (8,821,047,296 bytes)

Is this a problem? Should I be concerned that the copy was not completed correctly?
8 answers Last reply
More about size versus size disk
  1. Access the files from the target drive and make sure they work alright, if they do I wouldn't worry about it.
  2. Thanks Russel. I wish I could realistically do that but there are 4806 folders and 43674 files.

    Sounds like I may need to track down a file compare utility and run it overnight to determine any differences.

    Any recommendations?
  3. ok, I found a program called FolderClone. After messing with settings so that it copies everything instead of ignoring hidden/system files/folders, I got a clean run:

    2/17/2006 9:32:15 PM<Begin: compare D to H>
    2/17/2006 9:35:17 PM<End: compare D to H> {All Activity Logged}

    Regardless, I still have a difference:

    D (source)
    7.25 GB (7,790,862,336 bytes)

    H (target)
    8.22 GB (8,828,420,096 bytes)

    How can this be? Is it explainable?
  4. Looks like there is a difference between the two drives. Perhaps the way they are formatted?

    Anyway if you determine the files are copied correctly that's the big thing.
  5. D (internal) is NTFS.
    H (external) is FAT32.

    Is that the explanation? Is NTFS hgher density?
  6. There ya go! you found it.

    Those are totally different preparations when formatting.
  7. More than likely its the cluster size thats different between the two drives.
    If one drive is a 4k cluster and the other drive is say an 8k cluster then the same number of files will use up more space on the 8k drive.
    Reason for this is a 1k file will use 1 full cluster, 4k.
    So it would be 1k used in files but 4k total on disk. Hence the 8k cluster drive would use a full 8k to store that 1k file so you would be using 8k.

    only one file can use a cluster at a time. Thats why if your using a lot of very small files a small cluster size is best to lessen lost disk space.
    Bif files :ie 1mb or more, a larger cluster size is better.

    Note: mentioned cluster sizez may not be possible on actual drives. just for reference
  8. thanks very much
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