real size of the drive. Actual disk space used.

Discussion in 'Technical' started by ensens, Sep 27, 2010.

  1. ensens

    ensens Member


    I'm confused about disk space on my hard drive. The hard drive in question is simply used for storage and not for anything else (it is not the root filesystem). It is an ext3 drive.

    I would like to know if I reclaim any disk space on this drive. It is a 500 GB drive. But, when I run "df -h" it does not show up as a 500GB drive. It shows up as a "459GB drive".

    Here's the df command output:
    $ df -h
    Filesystem            Size  Used Avail Use% Mounted on
    /dev/sdb1             459G  409G   27G  94% /home
    It shows available only "27GB". I thought it should show 50GB "Avail".

    Is there a way to free up space on this drive? Is there a better tool to view the real details of this disk? Why does it show up as a 459GB disk when it's really a 500GB disk? Is there a way to free up space without deleting "data"?

    Thank you for your time and assistance.
  2. matty

    matty Member

    This can be because of block size and file size. If, for example, your disk is formatted with 4k blocks and you have lots of files that are less than 4k in size, you end up with slack space in the file system that can't be written to. If you type "man mke2fs", you'll see that you can tune your blocksize to suit the purpose of the filesystem at the time it is formatted. Don't attempt to change it with live data as you will wipe your filesystem.

    This is because manufacturers work in gigabytes, and computers work in gibibytes. They are different units of measurement.
  3. ensens

    ensens Member

    Thank you Matty!
  4. ensens

    ensens Member

    I ran tune2fs to reclaim some disk space on a drive only used for data.
    # tune2fs -m 0 /dev/sdb1
    tune2fs 1.41.11 (14-Mar-2010)
    Setting reserved blocks percentage to 0% (0 blocks)
    $ df -h
    Filesystem            Size  Used Avail Use% Mounted on
    /dev/sdb1             459G  409G   50G  90% /home

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