FAT real disk usage - Storage

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  1. FAT real disk usage

    How much real disk space do files and folders take on a hard drives
    using FAT (32 but please explain the differences if any)?

    Of course files occupy an integer number of cluster sizes (512B, 4KB
    or whatever the drive is formatted as). Besides these are there other
    structures used that take additional space (dynamically created)? And
    how much space does a directory take? Does it depend on the number of
    files it has underneath? Does it have data outside the FAT? I read
    some FAT specs but did not quite get this issues. Thank you.

  2. Re: FAT real disk usage

    On Mar 11, 4:55*pm, leibnizster wrote:
    > How much real disk space do files and folders take on a hard drives
    > using FAT (32 but please explain the differences if any)?
    >
    > Of course files occupy an integer number of cluster sizes (512B, 4KB
    > or whatever the drive is formatted as). Besides these are there other
    > structures used that take additional space (dynamically created)? *And
    > how much space does a directory take? Does it depend on the number of
    > files it has underneath? Does it have data outside the FAT? I read
    > some FAT specs but did not quite get this issues. Thank you.


    All files are directories are part of the FAT system. The only area
    outside of the FAT is the FAT itself, plus a few boot and BIOS sectors

    A typical cluster size on FAT disks is 16K. This means that any file
    between 1 byte and 16K will occupy 16K of the disk.

    A directory entry is always at least 32 bytes, and for long file names
    this will increase by increments of 32 bytes. Again the minimum size
    of a directory cluster will be typically 16K.

    For a disk with many small fies, the use of the disk is very poor.
    For a disk with a few large files, the useage is much better, though
    there is a 4GB limit on the maximum size of a FAT32 file

    Michael
    www.cnwrecovery.com

  3. Re: FAT real disk usage

    On Mar 11, 8:28 pm, "mscotgr...@aol.com" wrote:
    > On Mar 11, 4:55 pm, leibnizster wrote:
    >
    > > How much real disk space do files and folders take on a hard drives
    > > using FAT (32 but please explain the differences if any)?

    >
    > > Of course files occupy an integer number of cluster sizes (512B, 4KB
    > > or whatever the drive is formatted as). Besides these are there other
    > > structures used that take additional space (dynamically created)? And
    > > how much space does a directory take? Does it depend on the number of
    > > files it has underneath? Does it have data outside the FAT? I read
    > > some FAT specs but did not quite get this issues. Thank you.

    >
    > All files are directories are part of the FAT system. The only area
    > outside of the FAT is the FAT itself, plus a few boot and BIOS sectors
    >
    > A typical cluster size on FAT disks is 16K. This means that any file
    > between 1 byte and 16K will occupy 16K of the disk.
    >
    > A directory entry is always at least 32 bytes, and for long file names
    > this will increase by increments of 32 bytes. Again the minimum size
    > of a directory cluster will be typically 16K.
    >
    > For a disk with many small fies, the use of the disk is very poor.
    > For a disk with a few large files, the useage is much better, though
    > there is a 4GB limit on the maximum size of a FAT32 file
    >
    > Michaelwww.cnwrecovery.com


    So, a directory can occupy more than one cluster? What does this
    depend on? And for the directory table, is there a maximum number of
    characters allowed? Thank you.

  4. Re: FAT real disk usage

    leibnizster wrote:

    >So, a directory can occupy more than one cluster?


    Yes

    > What does this depend on?


    Just like any file, it depends on how much data needs to be stored.
    When one cluster is filled, another will be allocated.

    > And for the directory table, is there a maximum number of
    >characters allowed? Thank you.


    Directories are filled with entries. A directory entry (in FAT32) is
    32 bytes. Each file will take at least one entry, and files with names
    that don't fit the DOS 8.3 mold will take from two to thirteen
    entries, depending on the length of the name.

    For complete details, see the FAT32 specification at
    http://www.microsoft.com/whdc/system...re/fatgen.mspx

    --
    Tim Slattery
    MS MVP(Shell/User)
    Slattery_T@bls.gov
    http://members.cox.net/slatteryt

  5. Re: FAT real disk usage

    On Mar 12, 2:45 pm, Tim Slattery wrote:
    > Just like any file, it depends on how much data needs to be stored.
    > When one cluster is filled, another will be allocated.


    When is one cluster filled? When it holds too many entries? How does
    one compute the number of clusters it occupies if one knows the number
    of entries (subfolders and files) that it has?

  6. Re: FAT real disk usage

    leibnizster wrote:

    >On Mar 12, 2:45 pm, Tim Slattery wrote:
    >> Just like any file, it depends on how much data needs to be stored.
    >> When one cluster is filled, another will be allocated.

    >
    >When is one cluster filled? When it holds too many entries?


    Yes, when you need to add another entry and there's no room for it.

    > How does
    >one compute the number of clusters it occupies if one knows the number
    >of entries (subfolders and files) that it has?


    Divide cluster size by 32 to find out how many entries fit into a
    cluster. Divide total number of entries by that number.

    Total number of entries is not going to be easy to determine. As I
    said before, each file or subfolder takes from one to thirteen
    entries, depending on name length.

    --
    Tim Slattery
    MS MVP(Shell/User)
    Slattery_T@bls.gov
    http://members.cox.net/slatteryt

  7. Re: FAT real disk usage

    mscotgrove@aol.com wrote in
    news:e1eaef05-bf04-4650-bc62-c64fe4c7cc1f@s12g2000prg.googlegroups.com
    > On Mar 11, 4:55 pm, leibnizster wrote:
    > > How much real disk space do files and folders take on a hard drives
    > > using FAT (32 but please explain the differences if any)?
    > >
    > > Of course files occupy an integer number of cluster sizes (512B, 4KB
    > > or whatever the drive is formatted as). Besides these are there other
    > > structures used that take additional space (dynamically created)? And
    > > how much space does a directory take? Does it depend on the number of
    > > files it has underneath? Does it have data outside the FAT? I read
    > > some FAT specs but did not quite get this issues. Thank you.


    > All files are directories are part of the FAT system. The only area
    > outside of the FAT is the FAT itself, plus a few boot and BIOS sectors


    Bwahaha.

    >
    > A typical cluster size on FAT disks is 16K. This means that any file
    > between 1 byte and 16K will occupy 16K of the disk.
    >
    > A directory entry is always at least 32 bytes, and for long file names
    > this will increase by increments of 32 bytes. Again the minimum size
    > of a directory cluster will be typically 16K.
    >
    > For a disk with many small fies, the use of the disk is very poor.
    > For a disk with a few large files, the useage is much better, though
    > there is a 4GB limit on the maximum size of a FAT32 file
    >
    > Michael
    > www.cnwrecovery.com


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