RE: how to calculate correctly the cluster size

Discussion in 'Python' started by Tim Golden, Apr 21, 2004.

  1. Tim Golden

    Tim Golden Guest

    Josiah> The Windows 2k "Disk Administrator" software for
    Josiah> 2K always uses 4k cluster sizes by default.
    Josiah> I believe your varied cluster sizes are the
    Josiah> result of using Partition Magic to create them.

    FWIW, the FORMAT command does offer the possibility of selecting
    different cluster sizes. I've never used it personally (and I'm
    not about to try it on this machine, either!)

    <screen dump>

    FORMAT volume [/FS:file-system] [/V:label] [/Q] [/A:size] [/C] [/X]
    [...]

    /A:size

    Overrides the default allocation unit size. Default settings
    are strongly recommended for general use.
    NTFS supports 512, 1024, 2048, 4096, 8192, 16K, 32K, 64K.
    FAT supports 512, 1024, 2048, 4096, 8192, 16K, 32K, 64K,
    (128K, 256K for sector size > 512 bytes).
    FAT32 supports 512, 1024, 2048, 4096, 8192, 16K, 32K, 64K,
    (128K, 256K for sector size > 512 bytes).

    Note that the FAT and FAT32 files systems impose the
    following restrictions on the number of clusters on a volume:

    FAT: Number of clusters <= 65526
    FAT32: 65526 < Number of clusters < 268435446

    Format will immediately stop processing if it decides that
    the above requirements cannot be met using the specified
    cluster size.

    NTFS compression is not supported for allocation unit sizes
    above 4096.

    </screen dump>


    TJG


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    Tim Golden, Apr 21, 2004
    #1
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  2. > Josiah> The Windows 2k "Disk Administrator" software for
    > Josiah> 2K always uses 4k cluster sizes by default.
    > Josiah> I believe your varied cluster sizes are the
    > Josiah> result of using Partition Magic to create them.
    >
    > FWIW, the FORMAT command does offer the possibility of selecting
    > different cluster sizes. I've never used it personally (and I'm
    > not about to try it on this machine, either!)


    Indeed, you can change the cluster sizes using the command-line format
    command. However, when formatting a fresh drive using the format
    command at the command line, I would expect that it would do the same
    thing as the Disk Administrator, user cluster sizes of 4k if possible.
    For a FAT 32 drive, that range is 256 megabytes ... 8 terabytes.

    Why 4k? I don't know, maybe it strikes a nice balance between not
    having enough and having too many clusters, or maybe it is to mirror the
    4k/page size of many paging schemes in modern operating systems. A
    filesystem designer would probably be quite helpful at this moment.

    - Josiah
     
    Josiah Carlson, Apr 21, 2004
    #2
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