[Virtual server] Virtual Hard Drive: Weird behavior - Disk expanded after cleanup and defragmentation RRS feed

  • Question

  • Host OS = Windows 7 x64 
    Guest OS = Windows 2003 SP1 32-bit 
    Virtual Server 2005 R2 SP1 
    I had a dynamically expanding virtual disk with a current vhd file size of ~14GB (~13GB used disk space from within the Guest OS). 

    I then decided to convert my virtual server setup to have a base disk and a linked differential disk where I planned to make my current dynamically expanding disk as the base disk. Before I added on a differential disk, I cleaned up my base disk deleting all unwanted files, then defragmented my base disk (from within the virtual server). Now, from within the Virtual Server's guest OS, the used disk space declined from ~13GB to ~9GB. I had undo disk enabled at this time. I merged the undo disk when I shut down the guest OS. 

    However, to my surprise, the vhd file in the Host OS grew from ~14GB to ~20GB. I then repeated the defragmentation from within the Virtual Server guest OS with undo disk disabled. Even then the vhd file size continued to remain ~20GB. 

    After this, I ran compact vhd file twice from the Virtual Server administration website. Yet, the vhd file hardly shrunk from its ~20GB size. 

    Can anyone let me know why this anomalous behavior? Was there something wrong in the steps that I followed? 

    Thank You.
    Thursday, July 1, 2010 7:05 PM