Install Windows Server 2008 Update for Windows Server 2008 x64 Edition (KB956710) enhance Hyper-V role's support for processors and virtual machines to now support up to 24 logical processors and 192 virtual machines: http://www.microsoft.com/downloads/details.aspx?FamilyID=fe36823a-7e5a-4262-9bf5-d6b3ae3ad375.

Read more at http://support.microsoft.com/kb/956710.
Note:
To start a Windows Server 2008 x86-based virtual machine on a computer that uses a 6-core processor, you also have to install hotfix 950182.
For more information, view the article in the Microsoft Knowledge Base: http://support.microsoft.com/kb/950182/

Increased functionality and virtual machine control in the Windows Server 2008 Failover Cluster Management console for the Hyper-V role (KB 951308) is now available. The KB http://support.microsoft.com/?id=951308 describes the changes in the hotfx that update the Failover Cluster Management console (the Cluadmin.msc file) and server components of the failover cluster, including:

• Changes to the virtual machine view
  After you install this update, the actions for virtual computers are "online," "offline," "start," "stop," "shutdown," and "turnoff."
• Changes to virtual machine actions
  After you install this update, the only action in the Failover Cluster Management console for the Hyper-V role is Move Virtual Machines. This action causes each virtual machine that is in the running state to move by using the "save state" shutdown option. If the virtual machine is not in the running state, it does not have to be shut down, and its state will not change during the move.
• Allow for more than one virtual machine in a "Services or Applications" group
  After you install this update, the Failover Cluster Management console allows for more than one virtual machine. The High Availability Role Wizard for virtual machines identifies virtual machines that have files on the same disk and enables those virtual machines to be configured for High Availability. Therefore, the virtual machines will be in the same Services and Applications group. If the Services and Applications group moves to another node, all the virtual machines in that group are also moved.
• Add support for mount points or volumes without a drive letter
  After you install this update, the High Availability Wizard can detect when files for a virtual machine are on a volume that is using a mount point or a GUID instead of a drive letter. Additionally, the High Availability Wizard moves the appropriate disks into the same Service or Application group as the virtual machine resource.
• Changes to the virtual machine refresh action
  After you install this update, a refresh of a virtual machine in a group refreshes all the virtual machines in that group.
  Behavior changes if any node of the failover cluster has a disconnected virtual machine
• Fixes the conditions that gave you the error: "An error was encountered while loading the list of available virtual machine. Value cannot be null. Parameter name: managementObject."
• Behavior change when you add a pass-through disk to a virtual machine
  After you install this update, the Failover Cluster Management console correctly shows that the configuration change is not successful.
• Behavior change when the parent differencing disk is not on shared storage
  Differencing disks have parent and child relationships. When a differencing disk is configured, a parent disk is specified, and that parent VHD is required to be available for the child differencing disk to function. The parent and child VHDs must be on disks that are in the same Services or Applications group as the virtual machine resource.
  Before you install this update, if the parent disk is not located correctly, the virtual machine may not start because not all the VHDs are located on the same failover cluster node. This update detects the location of the parent VHD and provides a warning if the parent VHD is not on a disk that is configured for shared storage.
• Volume path copy
  This update lets the path of a storage volume to be copied from the properties of the disk resource in the Failover Cluster Manager console. When you configure a virtual machine, the paths of the volumes must be specified for the disks that will be used. After you apply this update, the path can be copied from the properties of the disk in the Failover Cluster Manager console. This is useful when the path is very long, such as when a volume uses a GUID instead of a drive letter.
  

See Also:

824684 (http://support.microsoft.com/kb/824684/LN/) Description of the standard terminology that is used to describe Microsoft software updates
950050 (http://support.microsoft.com/kb/950050/) Description of the update for the release version of the Hyper-V technology for Windows Server 2008

Taylor Brown's blog post shows you the WMI that will tell you what physical disk a virtual machine is using when configured for pass-thru on the host: http://blogs.msdn.com/taylorb/archive/2008/08/21/hyper-v-wmi-what-vhd-s-physical-disks

Hyper-V events are logged under "Application and Services Logs\Microsoft\Windows\Hyper-V-<component-name>"

- component-name could be:

• Config
• Integration
• VMMS
• Worker

Under the component node, you can find several types of event logs.

I want to point out one of the stumbling blocks that I encountered after installing the 32-bit version of KB950050 in order to use Hyper-V Manager to remotely administer a Hyper-V server (running Server Core).

According to the corresponding KB article:

Update for Windows Server 2008 (KB950050)
This 32-bit update package includes the release version of the following:

• The Hyper-V Manager console
• The Virtual Machine Connection tool for x86-based editions of Windows Server 2008

Based on my experience installing the Hyper-V Remote Management Update for Windows Vista (KB952627) and the note above from the KB article, after installing KB950050 on Windows Server 2008, I expected to be able to start MMC and add the Hyper-V Manager snap-in. However, it doesn't quite work that way.

To enable Hyper-V Manager after installing KB950050 for remote administration, you need to enable the corresponding feature:

1. Open Server Manager. (If Server Manager is not running, click Start, point to Administrative Tools, click Server Manager, and then, if prompted for permission to continue, click Continue.)
2. In Server Manager, under Features Summary, click Add Features.
3. In the Add Features Wizard, on the Select Features page, expand Remote Server Administration Tools, and then expand Remote Administration Tools
4. Click Hyper-V Tools, and then proceed through the rest of the wizard.

There is a new blog and Twitter aggregator (independent bloggers and 14 Microsoft bloggers on either TechNet or MSDN) for virtualization: VirtualizationFeed at http://www.virtualizationfeed.com/.

"Is my workload supported on Hyper-V?". Now the answer is posted in KB957006 (http://support.microsoft.com/?kbid=957006) Microsoft server software and supported virtualization environments. Rock on.
This article discusses the support policy for running Microsoft server software within the following supported virtualization environments:
•Windows Server 2008 with Hyper-V
•Microsoft Hyper-V Server 2008
•Supported partners' virtualization software
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
944987 (http://support.microsoft.com/kb/944987/) Support partners for non-Microsoft hardware virtualization software