Not all space available on USB storage devices after deleting partitions

Discussion in 'Mac Basics and Help' started by miretogo, Nov 11, 2014.

  1. miretogo macrumors newbie

    Joined:
    Aug 19, 2014
    #1
    I have two external USB storage devices:

    * 16 GB USB stick (flash drive)
    * Old 2.5 inch 80 GB HDD

    I performed the following procedure with Disk Utility on both devices:

    * Delete existing partition.
    * Create a maximum-size new partition.

    Afterwards, Disk Utility's "Partition" tab shows for both devices that about 5 GB are not available:

    * 16 GB USB stick: 10.06 of 15.47 GB available (-> 5.41 GB missing)
    * Old 2.5 inch 80 GB HDD: 74.1 of 79.68 GB available (-> 5.58 GB missing)

    Since about 5 GB are unavailable on both devices and since 5 GB is about the size of the last few Mac OS installers (Yosemite, Mavericks, etc.), I wonder if having used these devices in the past to install Mac OS has created something like hidden partitions that cannot be easily removed.

    What do you think?
     
  2. Weaselboy Moderator

    Weaselboy

    Staff Member

    Joined:
    Jan 23, 2005
    Location:
    California
    #2
    Try selecting the drive itself (like where it says Sandisk in my screenshot), and not just the partition. Then in the erase tab erase the entire disk. That should wipe anything on there.

    [​IMG]
     
  3. miretogo thread starter macrumors newbie

    Joined:
    Aug 19, 2014
    #3
    Thanks for your suggestion, Weaselboy. However, it doesn't seem to have any effect. For example, after erasing the USB stick, Disk Utility still states in the "Partition" tab that there is one partition named "Untitled", with a size of 15.47 GB, of which 10.06 GB are available.

    Screen Shot 2014-11-11 at 17.18.17.png

    PS: In the screenshot, "," is used as decimal mark instead of "." because I live in Germany.
     
  4. Weaselboy Moderator

    Weaselboy

    Staff Member

    Joined:
    Jan 23, 2005
    Location:
    California
    #4
    That blue shaded area in mine is out of whack also (showing about 1/3 in use on an empty drive) but when you select Untitled it shows the correct amounts for me. What do you see when you select the Untitled volume?

    Try running this command in Terminal and it will show what folders are there and how much space each uses.

    Code:
    sudo du -d 1 -x -c -g /Volumes/Untitled/
    I get this on a fresh erase.

    Code:
    1	/Volumes/Untitled//.fseventsd
    1	/Volumes/Untitled//.Spotlight-V100
    0	/Volumes/Untitled//.Trashes
    1	/Volumes/Untitled/
    1	total
    
    [​IMG]

    [​IMG]
     
  5. miretogo thread starter macrumors newbie

    Joined:
    Aug 19, 2014
    #5
    Thanks again for your reply, Weaselboy. Using your command, I get exactly the same output as you do.

    I think this phenomenon is too obvious to be a Disk Utility bug, so there must be another explanation.

    Using the instructions in this article (http://osxdaily.com/2011/09/23/view-mount-hidden-partitions-in-mac-os-x/), I discovered that there is also a partition called "EFI" (extensible firmware interface) on the USB stick. However, it has only a capacity of 209.7 MB.
     

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