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What triggers an increase in size on a "Dynamically Expanding Virtual Hard Disk"?

    Question

  • I have a virtual machine that is running Exchange 2010 on Windows 2008 R2.  The Hyper-V Host is running Windows Server 2012 R2.

    The virtual machine is setup with two disk drives, C: is the operating system drive and D: is the data drive.

    Yesterday I received an alert from our monitoring software saying the D: drive was down to less than 5% free space.  I logged on to the virtual machine to check it out and found that the C: drive is showing 66.5 GB of free space out of a total of 128 GB. The D: drive is showing 13.4 GB free out of a total of 255 GB.

    I then logged on to the host server and checked the settings on the virtual machine. When I checked the properties of the D: disk it showed me that it is configured as a "Dynamically Expanding Virtual Hard Disk" (VHDX Format) with a "Maximum Disk Size" of 512 GB.  It said that the current file size was 329.54 GB.

    Thinking that the VM may need to be restarted in order for Hyper-V to see that it needs more space and expand the disk I shutdown then started up the VM. The size remained the same as 255 GB.

    I thought that "Dynamically Expanding Virtual Hard Disks" would automatically increase in size up to the maximum. What must happen in order for the disk to be expanded?

    Chuck R.

    Tuesday, April 04, 2017 3:07 PM

Answers

  • Hi Sir,

    That disk should show the " maximum disk size " in VM operating system (in your case it would be 512 GB).

    I'd suggest you open disk management to check the disk size ( 255 might be the volume size not disk size ) .

    I suspect that 255GB D drive is only one partition of that disk . 

    Best Regards,

    Elton


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    • Marked as answer by Chuck_Rizzio Wednesday, April 05, 2017 1:04 PM
    Wednesday, April 05, 2017 7:58 AM
    Moderator

All replies

  • Hi Sir,

    That disk should show the " maximum disk size " in VM operating system (in your case it would be 512 GB).

    I'd suggest you open disk management to check the disk size ( 255 might be the volume size not disk size ) .

    I suspect that 255GB D drive is only one partition of that disk . 

    Best Regards,

    Elton


    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    • Marked as answer by Chuck_Rizzio Wednesday, April 05, 2017 1:04 PM
    Wednesday, April 05, 2017 7:58 AM
    Moderator
  • Elton, you are exactly right!!  I don't know why I didn't think to check "Disk Management".

    The disk had un-partitioned space equaling the difference between the allocated space and the "Maximum Disk Size".  I was able to extend the volume so all is good now.

    Thank you for bringing me back to my senses :-)

    Chuck R.


    Chuck R.

    Wednesday, April 05, 2017 1:04 PM