Hyper-V Server 2008 (Core) using Pass Though Disks to enhance Disk Performance

I have been looking deeper into Hyper-V Disk performance after very noticeable performance degradation when some of our database servers were virtualised.

It turns out I had set up the virtual hard disks (VHDs) in possibly the worst combination of options! To create the Virtual Machines (VMs) I had installed Windows Server 2008 Enterprise onto 1 dynamic VHD. I then set this to read only and created differencing disks to have 4 different VMs all sharing the original VHD as the base. This worked great and was certainly quick to set up. However, for production machines the disks should really be set from Dynamic to Fixed. This is not an option with differencing disks. I had also taken some snapshots which additionally degrades VHD performance.

With the plan to start again from scratch I went to my test server. This has Windows Hyper-V Server 2008 on it (i.e. not the Full windows server 2008 just the free core version of Hyper-V). I read about using Pass-Through Disks (PTDs) for database servers as they offer the best performance. The is a great video on how to do this at http://blogs.technet.com/mattmcspirit/archive/2009/02/27/new-virtualboy-tv-video-hyper-v-and-pass-through-disks.aspx. In Hyper-V R2 the fixed disk VHD is meant to almost match PTDs but as I can’t get my hands on R2 that isn’t an option for me.

Setting up the offline disk using diskpartTo start off I need to recreate my RAID array on the Host machine. I created the following logical drives.

  • 1 x Raid 1 50GB
  • 3 x Raid 5 at 20GB
  • 3 x Raid 5 60GB

I installed Hyper-V 2008 onto the Raid 1 drive and then connected to it via Hyper-V manager on my laptop (using Remote Server Administration Tools – RSAT)

Unfortunately, the logical drives did not show up in the “Add VHD” section. I had a feeling this is because they weren’t “initialized”. Normally I would do this through the Disk Management Console but this isn’t included in Hyper-V and cannot be done remotely either. It turns out I  have to use DISKPART on the Hyper-V Server command line

  • Log on to the Hyper-V desktop using “Remote Desktop”
  • go to the Command prompt and type “DISKPART”image
  • Select the disk you want to initialize/set offline. These are numbered from 0 (the host drive). “SELECT DISK 1”
  • Check there are no partitions on the disk by typing “DETAIL DISK”
  • Set the disk offline by typing “OFFLINE DISK”
  • Type “EXIT” to leave DISKPART and close the Remote Desktop Session
  • Go to the VM settings in the Hyper-V manager and the disks now show up

I now need to install the OS to the VM and check the disk performance actually has improved!

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Remote Server Administration Tools for Windows 7 – RSAT RTMs


Microsoft have released the final version of RSAT for Windows 7. Download RSAT here

Overview from Microsoft

Remote Server Administration Tools for Windows 7 enables IT administrators to manage roles and features that are installed on remote computers that are running Windows Server 2008 R2 (and, for some roles and features, Windows Server 2008 or Windows Server 2003) from a remote computer that is running Windows 7. It includes support for remote management of computers that are running either the Server Core or full installation options of Windows Server 2008 R2, and for some roles and features, Windows Server 2008. Some roles and features on Windows Server 2003 can be managed remotely by using Remote Server Administration Tools for Windows 7, although the Server Core installation option is not available with the Windows Server 2003 operating system.
This feature is comparable in functionality to the Windows Server 2003 Administrative Tools Pack and Remote Server Administration Tools for Windows Vista with Service Pack 1 (SP1).

This is a whopping ~220mb download and goes through the usual (IMHO) complicated installation method, i.e. install update, then go to windows components and find/tick the correct box. However, when installed you can use your lovely Windows 7 PC to manage your domain controllers 🙂

Despite my usual bugbear of the mix of full-size and small icons (see image) you actually get a whole new range of tools, most of which use powershell to do nifty tricks in the background, like the Active Directory Administration Centre. This looks very swanky and modern but will not do much unless you have the AD web service running (this is part of Server 2008 R2 – find out more on TechNet). Also, all the Terminal Services consoles have been given new names like Remote Desktop Services Manager. I don’t particularly like this as it blurs the line between client and server tools but that is the groovy new family-friendly Microsoft that is growing out of Redmond.

One word of warning if you have the beta version of RSAT. You must completely uninstall that first

Removing the complete Remote Server Administration Tools for Windows 7 pack
You must be either a member of the Administrators group on the computer from which you want to remove the Administration Tools pack, or you must be logged on to the computer by using the built-in Administrator account.
You can remove the complete Administration Tools pack from a computer by using the Uninstall a program utility in Control Panel.
To remove the Administration Tools pack
1. Click Start, click Control Panel, and then click Uninstall a program in the Programs area.
2. Click View installed updates.
3. Select Update for Microsoft Windows (958830).
4. Click Uninstall.


got a heads up from http://joeelway.spaces.live.com/blog/cns!2095EAC3772C41DB!2712.trak

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