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Archive for March, 2010

Hyper-v dynamic memory & Windows Virtual PC without hardware assisted virtualization

 

 

Great news these days from Microsoft Virtualization:

  1. Dynamic Memory allocation will be feature of new Service Pack for Hyper-V R2.
  2. Windows Virtual PC and XP Mode will run now on computers that don’t have hardware virtualization capabilities.

Surely those news are great, so let’s take a closer look what they actually mean

Dynamic Memory in Hyper-V

How memory works now in Hyper-V? Well high level description would be something like this: when you are creating virtual machines you assign some amount of memory to them and that’s it. Later on you can decide to assign more/less memory and then you should turn off virtual machine and do what you planned. Also with static memory assignment if you have Hyper-V host with 4Gb of RAM, and you plan to have 4 virtual machines with 1GB each, you could not start fourth virtual machines because lack of memory. That’s the main thing about static memory assignment – when you assign memory to virtual machine it will consume all that assigned memory from host, although current state of virtual machine only need half of that. So if you assigned 512 MB of RAM to virtual machine and while powered on that virtual machine only needs 256 MB of RAM, it will still consume whole 512 MB of RAM from the host. Ok, that is clear now, so let’s take a look how will dynamic memory assignment look like.

Although it is not yet completely disclosed, with dynamic memory you could assign more RAM to virtual machines and by that achieve better Hyper-V host utilization. So you could probably assign memory by using min and max values. Let’s describe that in particular scenario. Again, let’s take 4 virtual machines and host with 4 GB of RAM. With dynamic memory allocation you could assign to virtual machine memory with 512 RAM as minimum value and 1024 as maximum value. When you attempt to start virtual machines they would take as much memory as they need (512 or more), and other memory will be free in memory pool. In that scenario Hyper-V will manage further memory allocations based on virtual machine needs. So in some moment of time , one virtual machine would need 1024 MB, and Hyper-V will automatically assign that amount of memory. So, as you can see in this basic scenario, with dynamic memory, Hyper-V will be much more efficient.

 XP mode without Hardware virtualization

A lot of users wanted to try XP mode, but they couldn’t because they didn’t have computers with hardware virtualization support (a.k.a  Intel VT or AMD-V CPU). Now, those users also can try XP mode and for example use Internet Explorer 6 on Windows 7 as I described on one previous post.  If you would like to try Windows Virtual PC and XP mode and you don’t have hardware assisted virtualization, download update from Microsoft here (x86) or here (x64).