Q. How can I set the amount of memory reserved for the Hyper-V parent partition with Windows Server 2008 R2 SP1's dynamic memory?

A. There have always been some configurations to reserve a certain amount of memory for the parent partition, but the settings weren't always honored, leading to possible parent partition memory starvation. This memory shortage is especially a problem when you're running other applications in the parent partition (which you shouldn't do, but in some scenarios, such as running Server 2008 R2 on a laptop so you can demo, you probably need PowerPoint).

With dynamic memory, you now have a reliable way to ensure a certain amount of memory for the parent partition. The great news is that this value can be changed without requiring a reboot. If you need more memory for the parent, you can just change the value, and the memory manager will reclaim memory from dynamic memory-enabled virtual machines and allocate it to the parent. To set the values:

  1. Start the registry editor (regedit.exe).
  2. Move to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Virtualization.
  3. Select New, DWORD value from the Edit menu.
  4. Set the name to MemoryReserve then double-click it. Set the base to decimal and set the value to the amount of memory that should be reserved (in MB).
  5. Restart the Hyper-V Virtual Machine Management service (this is only needed once when you first create the value) using the Services (services.msc) management interface.

You can now change this value at any time to modify the memory reserved for the parent partition.

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