Release Notes: Important Issues in Windows Server 2012

Updated: May 31, 2012

Applies To: Windows Server 2012

[This topic is pre-release documentation and is subject to change in future releases. Blank topics are included as placeholders.]

These release notes address the most critical issues and information about the Windows Server® 2012 operating system. For information about by-design changes, new features, and fixes in this release, see documentation and announcements from the specific feature teams. For information about important steps to take before installing this release, including issues that you may need to work around, see Installing Windows Server 2012, a document available at the same location as this document. Unless otherwise specified, these notes apply to all editions and installation options of the Windows Server 2012.


You should be aware of the following issues affecting Single-Root I/O Virtualization (SR-IOV):

  • SR-IOV supports only 64-bit guest operating systems, either Windows Server 2012 or 64-bit versions of Windows® 8 Release Preview. In addition, SR-IOV requires both hardware and firmware support. If you configure a guest operating system to use SR-IOV and either the hardware or firmware is not supported, the Network tab in Hyper-V Manager will show Degraded (SR-IOV not operational). Contact your system manufacturer to determine if your system supports SR-IOV, as well as the required BIOS version and settings to enable memory and interrupt remapping.

  • Even with the supported hardware and all appropriate firmware, BIOS settings, and network drivers configured, the Network tab in Hyper-V Manager for a selected virtual machine might show Degraded (SR-IOV not operational). In this circumstance, check the event log for event 12607 in Application and Services\Microsoft\Windows\Hyper-V-SynthNic\Admin with this text: ‘VMName’ Network Adapter ({GUID}) is configured to use SR-IOV but that capability is disabled by policy on this machine. (Virtual Machine ID {GUID}).

    If this occurs, first check with the system manufacturer to determine if a BIOS update is available. If no update is available, run the following command from an elevated command prompt, and then restart the physical computer:

    reg add "HKLM\Software\Microsoft\Windows NT\CurrentVersion\Virtualization" /v IOVEnableOverride /t REG_DWORD /d 1


    After the computer restarts, you will find event 24012 in the event log, warning you that the system is vulnerable and could experience reduced performance or system instability. Although SR-IOV might function, this warning is valid and you should assign SR-IOV devices only to virtual machines that run trusted workloads (or do not use SR-IOV).

  • If the Network tab in Hyper-V Manager still shows Degraded (SR-IOV not operational) and you do not find event 12607 in the event log, run the Windows PowerShell commands below from an elevated Windows PowerShell prompt to get further information on the cause:


    If the cause is related to the platform, the properties IovSupport and IovSupportReasons will contain further information.

    get-vmswitch * | fl *

    If the cause is related to the physical network adapter or driver, the properties IovSupport and IovSupportReasons will contain further information.

    get-vmnetworkadapter * | fl *status*

    If the cause is related to the virtual network adapter, the properties Status and StatusDescription will contain further information.

Server Manager

  • If you install a role service or feature using a method other than Server Manager (such as DISM.exe or an Unattend.xml file) and did not install all of its dependencies and then later install a different role service or feature using Server Manager or a Server Manager Windows PowerShell cmdlet, in some cases the original role service or feature will be unintentionally uninstalled. To avoid this, use only Server Manager or Server Manager PowerShell cmdlets to install server roles, role services, and server features. If this has already occurred, use Server Manager (or Server Manager PowerShell cmdlets) to reinstall the item that was uninstalled.

  • After a server has been added to the Server Manager server pool, if a Best Practices Analyzer scan has never been run on the server, Server Manager displays a red Manageability status indicator in the server’s thumbnail on the dashboard page. To resolve this issue, run a Best Practices Analyzer scan on servers after adding them to the Server Manager server pool.


  • If you use storage spaces that use the parity resiliency type and then install this release of Windows Server 2012, the data in those storage spaces will not be accessible. To avoid this, back up data stored in those storage spaces and delete the storage spaces before installing this release. After installation is complete, re-create the storage spaces and restore the data.

  • Storage spaces that are not in the “healthy” state prior to installing this release may never complete repair operations after installation. To avoid this, ensure that repair operations have completed on all storage spaces and they are in the “healthy” state prior to installation. You can check the health of a storage space with the HealthStatus property reported by the Get-VirtualDisk Windows PowerShell cmdlet. command.

  • If you delete a clustered storage pool, cluster resources which depend on the storage pool will go offline and may become permanently unavailable. To avoid this, only delete a clustered storage pool when it is on a node with the cluster resource for the pool in the “online” state.

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