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EXT4 File-System Updated For Linux 3.9

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  • EXT4 File-System Updated For Linux 3.9

    Phoronix: EXT4 File-System Updated For Linux 3.9

    The EXT4 file-system in the forthcoming Linux 3.9 kernel will support using the previously-introduced punch hole functionality for inodes not using extent maps...

    http://www.phoronix.com/vr.php?view=MTMxMjk

  • #2
    From the article:
    Hole punching as it pertains to file-systems is marking a portion of a file as being no longer needed and can then be reclaimed.
    I think it's not true.
    Afaik hole punching is about _virtually_ allocating space for a big file but physically only doing so when one is writing to it and only as much as has been written.

    E.g. when you create a vmware virtual image of like 10GB for a Linux OS that uses only like 4GB when fully installed you'll actually be using just 4GB on your HDD while the vmware installed image file ".vmdk" claims/thinks it's 10GB.
    This also has some drawbacks, like when the guest OS tries to use the rest of the "free" space while the disk is already full.

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    • #3
      Originally posted by mark45 View Post
      From the article:

      I think it's not true.
      Afaik hole punching is about _virtually_ allocating space for a big file but physically only doing so when one is writing to it and only as much as has been written.

      E.g. when you create a vmware virtual image of like 10GB for a Linux OS that uses only like 4GB when fully installed you'll actually be using just 4GB on your HDD while the vmware installed image file ".vmdk" claims/thinks it's 10GB.
      This also has some drawbacks, like when the guest OS tries to use the rest of the "free" space while the disk is already full.
      I may be wrong, but I'm pretty sure you're thinking about sparse files, which ext4 already supports

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