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Hyper-V, shouldn't a dynamic disk grow dynamically?

The host is "Windows Server 2012 Standard" with Hyper-V role enabled.
I created a 50GB "dynamic VHDx" then installed Windows 2003 Server on it for testing. There is only one partition C: drive. On this partition, there is 40GB+ available space after the OS was installed.
Now I connected a USB hard drive to host, made this USB hard drive offline, then attached this USB hard drive to this VM.
Then, I am trying to copy a 70GB file from the USB hard drive to C: drive within this VM, I got an error message saying that I do not have enough space.

So I shut down the VM, "Expanded" the VHDx, Tried to increase C: drive to take the additional space, failed. I would have to create a separate partition for this additional space.

My questions are
- Since I am using Dynamic VHDx, I expect it will grow dynamically to accept a large file when there is not enough space. But it looks like I am wrong. Why?
- I guess I cannot increase C: partition because it holds OS but I should be able to increase a data partition. Is this correct?

2 Solutions
Cliff GaliherCommented:
When you specify a size on a dynamic disk, you are specifying a maximum. So a 50GB disk expand up to 50, but not larger. Which means copying a 70GB file will clearly fail. As far as the partition, dynamic disks don't change the underlying limits of the guest OS. If you couldn't expand a partition because of a second partition in a physical install with physical disks, a dynamic disk doesn't suddenly change that rule. The guest doesn't know or see the disk as virtual. It treats it no differently than it would a physical disk. 2003 only allows expanding the system partition under very specific circumstances, so you are likely simply hitting that block. Nothing to do with the fact that your disk is dynamically expanding.
If you increased the size of the virtual disk you will have to boot the VM using a 3rd party partitioning tool, like GParted, in order to also extend the VM's partition. System partitions where the OS is on can't be extended from within the OS directly, only data partitions can be extended that way.

This was changed with newer OS's, like 2008 server or Vista, there you can also extend the system partition directly from within diskmanagement.
techcityAuthor Commented:
Thanks very much!
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