Windows 10 and Hyper-V dynamic memory

  1. Posts : 66
    Windows 10 Pro x64 version 20H2

    Windows 10 and Hyper-V dynamic memory

    It seems that Windows 10 does not behave nicely in a Hyper-V virtual machine, also running on Windows 10.

    My laptop has plenty of memory and is running Windows 10 build 10586.63.

    Normally I configure a new VM with dynamic memory enabled, because I saw no reason why not. Now I found one: Windows 10 as client OS does not like that. All my Windows 10 VM's reported only about 1.5 GB usable with 4 GB configured. Not surprisingly, they were all dead slow.

    When I disabled dynamic memory in the settings, the problem went away.

    This may severely limit the number of VM's you can be running simultanously!

      My Computer

  2. Posts : 17,641
    Windows 10 Pro

    Of course a Hyper-V vm becomes slower if you use dynamic memory with default settings. The Hyper-V will be constantly monitoring the demand and assign the required RAM to the vm.

    For the dynamic memory to work you need to assign enough startup memory (#1 in screenshot below), increase the the memory buffer (#2) and memory weight (#3):

    Windows 10 and Hyper-V dynamic memory-2016_01_24_16_58_091.png

    A Windows 10 virtual machine needs surprisingly little RAM to function well. Here in the screenshot the memory usage of a Windows 10 vm otherwise idle at the moment, only running Macrium to create a system image. Memory demand only 522 MB but because I have assigned a 35% buffer, it's using 768 MB of the assigned maximum 8 GB:

    Windows 10 and Hyper-V dynamic memory-2016_01_24_17_03_572.png

    The buffer is important: When using dynamic memory and the demand suddenly increases for example due a resource heavy application being launched, it takes time for Hyper-V to assign more RAM to the vm. The bigger the buffer, the better the vm reacts to increased demand.

    Dynamic memory should only be used when it really is needed, for instance when it is important to have multiple virtual machines running at the same time. Dynamic memory should not be used when installing Windows, it can make the time needed for installation somewhat longer.

    Generally speaking a Windows 10 vm with 2 GB of static RAM assigned works faster than the same vm with 512 MB to 4 GB dynamic RAM.

      My Computer

  3. Posts : 66
    Windows 10 Pro x64 version 20H2
    Thread Starter

    Thank you for your excellent explanation!

    I will keep this in mind, but generally will follow your advice to not use dynamic memory unless I really need it.


      My Computer

  4. Posts : 17,641
    Windows 10 Pro

    You are welcome :)
      My Computer


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