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Size vs Size on disk

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  • Size vs Size on disk

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ID:	508668 Hello,

    Does anyone know why there is a difference in value between those two measures: "Size" and "Size on disk" , on the properties of a file ?

    (I attach an image for clarification purposes)

    Thanks in advance.
    -
    Madrid (Spain).

  • #2
    Disks store information in blocks, so a 1 byte file would still occupy a block (normally 4kb)
    Tom Jones
    MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
    PhD, MSc, FIAP, MIITT
    IT Trainer / Consultant
    Ossian Ltd
    Scotland

    ** Remember to give credit where credit is due and leave reputation points where appropriate **

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    • #3
      So, the real size would the "size on disk" ?
      -
      Madrid (Spain).

      Comment


      • #4
        Not necessarily
        In your example, the actual file is 26.9Kb - on a disk with 4K blocks (clusters), it is 28Kb, on a disk with 8K blocks, it would be 32Kb
        See https://support.microsoft.com/en-gb/kb/140365 for default cluster sizes
        Tom Jones
        MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
        PhD, MSc, FIAP, MIITT
        IT Trainer / Consultant
        Ossian Ltd
        Scotland

        ** Remember to give credit where credit is due and leave reputation points where appropriate **

        Comment


        • #5
          Originally posted by Ossian View Post
          Not necessarily
          In your example, the actual file is 26.9Kb - on a disk with 4K blocks (clusters), it is 28Kb, on a disk with 8K blocks, it would be 32Kb
          See https://support.microsoft.com/en-gb/kb/140365 for default cluster sizes
          Thanks a lot for the explanation and the link!
          -
          Madrid (Spain).

          Comment

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