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Things You Have To Know Before Natively Booting Into VHD

    General discussion

  • Hi,

    Could somebody please confirm that Windows automatically expands the VHD drive to the specified maximum size of the dynamic VHD when natively booting into the VHD?

    Here's what I am talking about. I decided to install Windows Developer Preview (WDP) into a VHD. To do that, I created the VHD from the WDP's installation wizard by pressing SHIFT+F10 and typing:

    E:>diskpart
    DISKPART>create vdisk file=d:\vm\wdp\wpd.vhd type=expandable maximum=60000

    I believed this will create a null-sized VHD file that will be filled by system little by little until the specified limit of 60,000 megabytes is reached. That is, I thought, if installer had to write one byte to my created VHD file (suppose), I would have a file of 1 byte when the OS boots from this VHD.

    It seems like I was totally wrong. When the OS is inactive (shutdown), the VHD file will consume as many bytes as is written to it. That is, if, after installing, the WDP consumes 8+ Gbytes of data, the VHD file will have different sizes depending on whether you check the size from the WDP or from Windows 7:

    1. [Windows 7] The VHD is 8+ Gbytes in size.

    2. [Windows Developer Preview] The VHD is 58,6 Gbytes in size!

    In other words, I seems like the OS automatically expands the VHD drive to its limit when natively booting into it.

    This is confirmed by the fact that creating a VHD with size limit which is greater than the size of the physical drive partition used to store that VHD drive and attempting to install the WDP on this VHD drive leads to VHD_NOT_ENOUGHT_DISK_SPACE error once you first boot into the OS after setup is finished copying files!

    Could you please confirm my assumption that native VHD booting radically differs from booting in the VHD from Hyper-V in terms of managing the space. When booting into VHD from Hyper-V never expands the VHD, native booting from BIOS/UEFI ALWAYS expands the VHD to its maximum size.

    Thank you.


    Well this is the world we live in And these are the hands we're given...
    Tuesday, September 20, 2011 12:57 PM