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High Memory Utilization on Windows Guest on Hyper-V 2012 Server

    Question

  • Hi All,

    We have installed Hyper-V 2012 Datacenter Server having 64 GB ram on physical Server, we have created three Virtual machines of Windows Enterprise 2008 R2 SP1 with 16 GB or ram each,we have configured dynamic memory but all three VM's are utilization memory above 95 % constant, for the same we have installed latest integration services but still utillization is high.

    And check the process also no process found that can be suspected for high mem utilization.

    So need help how to configure dymanic memory and how to set buffer setting options for 16 GB of ram.

    Regards,

    Sudhir

    Friday, July 12, 2013 6:26 AM

Answers

  • Within the Hyper-V settings for one of your VM's, what settings are currently configured within the memory settings? What's listed under Startup RAM, Minimum RAM, Maximum RAM and Memory buffer?

    By default when you create the VM the amount of memory you specify during the creation process is configured within the settings as the Startup RAM value, NOT the Maximum RAM value. On one of my VM's for instance, I configured it with 2048MB ram and enabled dynamic memory. Within the settings the max ram defaults to 1,048,576MB, so if the VM wants / needs more memory it's free to take it up to 1TB (if that's available, which it isn't on my machine). On one my test machines configured with 2GB I've had it using up to more than 4GB at times.

    If you haven't already done so I'd suggest you need to adjust the Maximum RAM setting to a smaller value, closer to what you're looking for.

    Also note, with the default buffer value of 20%, if your VM NEEDS say 10GB currently, it will automatically grab 12GB if that's available, so that could also explain why you're seeing such high utilization.

    Friday, July 12, 2013 9:05 AM
  • Dynamic Memory is a great tool to help you understand your workloads.

    If the VM is always demanding more memory, you have an application that is constantly consuming as much memory as it can get and not returning any.  Older versions of SQL, the Exchange Mailbox role (again, older versions) are MSFT examples of this.

    Now, another question.  Where are you looking to see that the VM's utilization is constantly above 95%?

    Another thing that I have noticed, is that if you use SCOM and Dynamic Memory - you will quite frequently get SCOM alerts as the applications in the VM demand more RAM, and then when you check the VM everything looks fine.  The solution is to tune the alert.  As this alert is tossed in only the moment that the application demands RAM and Hyper-V gives it (a very brief moment in time).


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.
    Disclaimer: Attempting change is of your own free will.

    Friday, July 12, 2013 3:17 PM

All replies

  • Within the Hyper-V settings for one of your VM's, what settings are currently configured within the memory settings? What's listed under Startup RAM, Minimum RAM, Maximum RAM and Memory buffer?

    By default when you create the VM the amount of memory you specify during the creation process is configured within the settings as the Startup RAM value, NOT the Maximum RAM value. On one of my VM's for instance, I configured it with 2048MB ram and enabled dynamic memory. Within the settings the max ram defaults to 1,048,576MB, so if the VM wants / needs more memory it's free to take it up to 1TB (if that's available, which it isn't on my machine). On one my test machines configured with 2GB I've had it using up to more than 4GB at times.

    If you haven't already done so I'd suggest you need to adjust the Maximum RAM setting to a smaller value, closer to what you're looking for.

    Also note, with the default buffer value of 20%, if your VM NEEDS say 10GB currently, it will automatically grab 12GB if that's available, so that could also explain why you're seeing such high utilization.

    Friday, July 12, 2013 9:05 AM
  • Dynamic Memory is a great tool to help you understand your workloads.

    If the VM is always demanding more memory, you have an application that is constantly consuming as much memory as it can get and not returning any.  Older versions of SQL, the Exchange Mailbox role (again, older versions) are MSFT examples of this.

    Now, another question.  Where are you looking to see that the VM's utilization is constantly above 95%?

    Another thing that I have noticed, is that if you use SCOM and Dynamic Memory - you will quite frequently get SCOM alerts as the applications in the VM demand more RAM, and then when you check the VM everything looks fine.  The solution is to tune the alert.  As this alert is tossed in only the moment that the application demands RAM and Hyper-V gives it (a very brief moment in time).


    Brian Ehlert
    http://ITProctology.blogspot.com
    Learn. Apply. Repeat.
    Disclaimer: Attempting change is of your own free will.

    Friday, July 12, 2013 3:17 PM
  • Thanks Brian,

    Looking in task manager under performance tab, currently we are using SQL application and my question is that in dyanmic settings the ram we have allocated in minimum for example it is 2048 MB and maximum is 16 GB still in task manager in memory performance it shows that Server is having only 2048 MB and the utilization is shown for 2GB and not for 16GB.

    Sunday, July 14, 2013 10:30 PM