Hyper-V Disk Space Planning RRS feed

  • Question


    Recently we had a virtual server run out of space on the host server causing the virtual server to pause critical. We moved the Virtual machines onto a NAS, then added additional hard drives to the server and rebuilt the raid to double the size of the volume containing the virtual servers, then moved the virtual servers back to the host server on the larger volume.

    The disks were set to dynamically expand but not to exceed a predefined limit that was less than the size of the volume. It was the .BIN files that exceeded the physical volume stopping the server.

    My question is, Is there a guideline or basis to use when planning hard drive space on the host server for Virtual Servers. How much space should be left on the host, assuming the VHD files will not grow passed a pre-defined limit? How much space should be there for the Virtual machine itself and its configuration files including the BIN files? And if there is no snapshot should these files continue to grow over time or remain a consistent size?


    Thank you all for your time and thoughts on this matter.



    Thursday, December 30, 2010 8:19 PM

All replies

  • Hi Ronnie!

    When you set the disk size of a vhd you also allow to grow up to that amount. If you set the vhd type to "fixed size", the storage space will be allocated from the start and the vhd will not expand further. Unless you manually expand the size of the vhd. This is the best practice setup of a vm that will be having intense disk activity, such as SQL servers.

    If you create a dynamically expanding vhd with not enough physical storage to allow it to grow to its full amount, is called "thin provisioning" and is commonly used in a HA clustered SAN environment. Meaning that several VM's share a SAN storage. Usually you expand the physical SAN storage when needed "on-the-fly" without having to shut down the vm that demands increased storage.

    One thing that I personally practice is: Even if you do not have enough storage at the time of deployment and if your vhd can and most likely will grow out of physical storage, make sure that you will be able to expand it when it does.

    The size of the other files (such as bin etc) however, may vary. These are usually paging files and will vary in size, depending on how much RAM and virtualized hardware you have assigned to the VM.

    Microsoft recommends that you run the MAP toolkit when planning a virtual environment.



    Please let me know if this wasn't the answer you were looking for, and I will try to help you as best as I can.

    / Ogge

    Thursday, January 6, 2011 10:15 AM