Tag Archives: Hyper-V

How to tell if your CPU Supports SLAT

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SLAT-enabled processor is the requirement of Hyper-V RemoteFX feature which is introduced in Windows Server 2008 R2. It’s the requirement of Windows 8 client Hpyer-V feature as well.

For INTEL CPU models, following CPU models are SLAT-Capable

  • Server: E5500 or higher.
  • Desktop/Laptops: I3/I5/I7/I7-qm

There is a handy tool named CoreInfo from systeminternals that can check if your CPU is SLAT-Capable, it’s pretty easy to use:

  1. Download from http://technet.microsoft.com/en-us/sysinternals/cc835722
  2. Launch an elevated command prompt
  3. Run “CoreInfo.exe -v”

If you see EPT  Supports Intel extended page tables (SLAT) then you are good.

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References:

Hyper-V: List of SLAT-Capable CPUs for Hosts

Understanding High-End Video Performance Issues with Hyper-V

Hyper-v Tip: Use windows key without fullscreen

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When connect to a remote VM with hyper-v manager, I have to full screen to make Windows key. Personally I think Hyper-V should have a Windows key button in toolbar like "Ctrl+Alt+Delete" button.

Actually Hyper-v manager allows you to select where the Windows keys goes when you press it. Open up the Hyper-V Settings dialog from with the Hyper-V Manager and go to the keyboard setting, you will see 3 settings.

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  1. Use on the physical computer
  2. Use on the virtual machine
  3. Use on the virtual machine only when running full-screen

The default one is #3. Once you change it to #2, you will be able to use Windows key inside VM without *full-screen* it.

You will find this helpful if you are connecting to a VM has Windows 8 Metro UI enabled. Without a windows key it’s hard to exit Metro style app and go back to start screen.

How to turn on client hyper-v in Windows 8

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In Steven Sinofsky’s this blog – Bringing Hyper-V to “Windows 8”. He talks about that Windows 8 will support virtualization on the "client" OS.  This is very helpful for developers as they typically have the need to setup additional test environment on their PC.

How to turn on client hyper-v in Windows 8

First, make sure your system meets the client hyper-v virtualization requirement, you have 64bit windows 8 OS and SLAT available on CPU.

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  1. Control Panel –> Programs
  2. Turn Windows Features On or Off
  3. Check Hyper-V, Click Ok

Note: If your system does not have the required virtualization support, the client Hyper-V feature will be greyed out. To check if your CPU is SLAT-capable, check this How to tell if your CPU Supports SLAT.

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The other cool thing is you can turn hyper-v on even if you are booting from VHD. This behavior is same server Hyper-V in Windows Server 2008 R2.

IDE/ATAPI Account does not have sufficient privilege to open attachment

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You might get following error after you move or replace a virtual disk drive file of a hyper-v virtual machine.

An error occurred while attempting to start the selected virtual machine(s).
‘TestVM’ failed to start.
Microsoft Emulated IDE Controller (Instance ID
{83F8638B-8DCA-4152-9EDA-2CA8B33039B4}): Failed to Power on with Error ‘General
access denied error’
IDE/ATAPI Account does not have sufficient privilege to open attachment
‘D:\VM\TestVM\TestVM.vhd. Error: ‘General access denied error’
Account does not have sufficient privilege to open attachment
‘D:\VM\TestVM\TestVM.vhd. Error: ‘General access denied error’

This is because the permissions on the new virtual hard drive (D:\VM\TestVM\TestVM.vhd in this case) are incorrect. Here is the steps to fix this permission file.

  1. Open Hyper-V manager, Right click settings of the virtual machine,
  2. Find the Virtual Hard Drive and choose "Remove".
  3. Re-add the same Virtual Hard Drive back to the machine.
  4. Now start the VM again, it should boot successfully.

Install Remote Server Administration Tools on Windows 7 SP1

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Remote Server Administrator Tools (RSAT) is not compatible with Windows 7 SP1. If you install Remote Server Administration Tools on Windows 7 SP1 slipstreamed media, you will get following error.

The update is not applicable to your computer

That’s because current RSAT version only supports Windows 7 RTM. To workaround this issue, you can Install Remote Server Administration Tools before installing Windows 7 SP1. The SP1 upgrade will update RSAT to SP1 version. The other option is wait for official release of Remote Server Administrator Tools for windows 7 SP1, which will happen this April.

Update 4/8/2011: Microsoft released Windows 7 SP1 RSAT Tools to public today. The download link is here http://www.microsoft.com/downloads/en/details.aspx?FamilyID=7d2f6ad7-656b-4313-a005-4e344e43997d

Windows Server 2008 R2 SP1 New Features

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Other than rolls up all previous released windows patches since RTM, Windows Server 2008 R2 SP1 contains two new features. Dynamic Memory and RemoteFX.

Dynamic Memory

Dynamic Memory is a memory management feature for Hyper-V VM administrators. Dynamic Memory allows administrator allocates a range of memory to indivual VMs and windows system will automatically adjust memory of each VM based on performance.

RemoteFX

RemoteFX creates a local like experience for remote users, including windows Aero and 3D contents.

You can read more about SP1 from Windows 7 Team Blog

Hyper-V VM Slow on Windows Server 2008 R2

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I recently upgraded my virtual machine hosting server from Window Server 2008 to Windows Server 2008 R2. There are some noticeable performance drop, especially on virtual machines that handles big log files, the automation script execution time can take 200% or more than it was in a VMHOST with Windows Server 2008.

I have done some testing and the performance downgrade seem introduced by the new power management system in windows server 2008 R2. There are 3 build in power plan in Windows Server 2008 R2

  • Balanced (recommended)
  • High Performance
  • Power Saver

The default power plan in Windows Server 2008 R2 is Balanced. After I change Power Plan to High Performance and the performance downgrade issue does no occur any more. My guess is when power plan is set to balance, applications might not full utilize all available hardware resources.

You can also checkout this post for Set the power configuration to High Performance in scripts.

Limitations you need know before installing Hpyer-V on laptop

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If you are thinking about installing Hyper-V on laptop, you need to put following into consideration. Some of Hyper-V’s design will limit laptop’s functions, these limitation are reasonable for a server operation system but would be a pain when you consider installing Hyper-V on a laptop.

You cannot connect a virtual network to a wireless network adapter

As a result, you cannot provide wireless networking capabilities to virtual machines. if you mainly use wireless NIC or all communication between the VM and the outside world would have to be through the Wireless NIC, this will turn out to be a great deal.

Power-saving features are disabled after Hyper-V role is enabled

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