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How to Configure Memory for a Virtual Machine

Updated: March 16, 2011

Applies To: Virtual Machine Manager 2008, Virtual Machine Manager 2008 R2, Virtual Machine Manager 2008 R2 SP1

You can specify the amount of memory that you want to allocate on a host for a new virtual machine, or specify whether to use the Dynamic Memory feature available in Virtual Machine Manager (VMM) 2008 Service Pack 1 (SP1) by using the following procedures. You can use these procedures when you modify a virtual machine or template, or configure hardware profile settings from the New Template Wizard, the New Hardware Profile Wizard or the New Virtual Machine Wizard.

noteNote
These settings are available on the Hardware Configuration tab in the properties of a virtual machine or template, on the Hardware Settings tab in the New Hardware Profile wizard, or on the Configure Hardware page of the New Template Wizard or the New Virtual Machine Wizard.

In VMM 2008 or VMM 2008 R2, you can specify the amount of memory that you want to allocate on a host for a new virtual machine by using the following procedure.

To configure memory for a virtual machine (VMM 2008 and VMM 2008 R2)

  1. In the left pane, under Hardware Profile, click Memory.

  2. Modify the setting as follows:

    Virtual machine memory. Specify, in megabytes (MB) or gigabytes (GB), the total amount of memory on the host that you want to allocate to a virtual machine. The maximum amount of memory that is available to each virtual machine memory depends on the virtualization platform.

     

    Virtualization Software Minimum Memory Maximum Memory

    Hyper-V (Windows Server 2008 R2 and Windows Server 2008

    8 MB

    64 GB

    Virtual Server

    4 MB

    3.6 GB

    VMware ESX Server 3.5 and ESX Server 3i

    4 MB

    64 GB

    VMware ESX Server 3.0.2

    4 MB

    16 GB

In VMM 2008 R2 SP1, you can configure a virtual machine to use static memory or the new Dynamic Memory feature. Additionally, you can configure the memory priority. You can configure memory settings by using the following procedure.

ImportantImportant
To use Dynamic Memory, the virtual machine must be running a guest operating system that supports Dynamic Memory. Additionally, the virtual machine must be placed on a Hyper-V host that is running Windows Server 2008 R2 with Service Pack 1. For more information about the requirements for Dynamic Memory, see What's New in Virtual Machine Manager 2008 R2 SP1.

To configure memory for a virtual machine (VMM 2008 R2 SP1)

  1. In the left pane, under Hardware Profile, click Memory.

  2. In the right pane, select one of the following options:

    noteNote
    If the virtual machine is in a running state, the only memory settings that you can change are the memory buffer percentage value and the memory priority. To modify other memory settings, the virtual machine must be turned off.

    • Static. In the Virtual machine memory box, specify in megabytes (MB) or gigabytes (GB) the total amount of memory on the host that you want to allocate to a virtual machine. See step 2 of the previous procedure for information about maximum memory limits for each virtualization platform.

    • Dynamic. If you select this option, memory is dynamically assigned to the virtual machine based on demand. You can also configure the following settings:

       

      Setting Description Values

      Startup memory

      Specifies the memory required to start the virtual machine (in MB or GB). The value must be high enough to enable the guest operating system to start, but should be as low as possible to allow for optimal memory utilization and potentially higher consolidation ratios.

      Valid range: Even number between 8 MB – 64 GB. Must be less than or equal to maximum memory. By default, startup memory is set to what was originally allocated for static memory.

      Maximum memory

      Specifies the maximum amount of memory that the host can allocate to the virtual machine (in MB or GB). You can set the value from as low as the value for startup memory to as high as 64 GB. However, a virtual machine can use only as much memory as the maximum supported by the guest operating system. For example, if you specify 64 GB for a virtual machine that is running an operating system that supports a maximum of 32 GB, the virtual machine cannot use more than 32 GB.

      Valid range: Even number between 8 MB – 64 GB. Must be greater than or equal to startup memory. By default, the value is 65536 MB.

      Memory buffer (%)

      Specifies the preferred memory buffer of the virtual machine (as a percentage). Hyper-V uses performance counters in the virtual machine that identify committed memory to determine the current memory requirements of the virtual machine and then calculates the memory to add as a buffer. For more information, see the Hyper-V Dynamic Memory Evaluation Guide (http://go.microsoft.com/fwlink/?LinkId=196615).

      noteNote
      The buffer is not maintained when there is not enough physical memory available in the computer to give every virtual machine its requested memory buffer.

      Valid range: 5% – 2000%. By default, the buffer is 20%.

You can also assign a priority for the virtual machine when allocating memory on the host. When memory usage on a host is high, virtual machines with higher priority are allocated memory resources before virtual machines with lower priority. Also, a higher priority virtual machine will start before a lower priority virtual machine. For information about how to configure memory priority, see How to Configure Virtual Machine Priority and Availability.

TipTip
You can view information about memory usage in Virtual Machines view in the VMM Administrator Console. To do this, right-click the column header row, and then add the Startup Memory, Assigned Memory, Memory Demand, Memory Status and Maximum Memory columns.

See Also

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