Article ID: 2853952 - View products that this article applies to.
For example, assume that you have a virtualized domain controller on a Hyper-V host server. When the Hyper-V host server crashes or encounters a power outage, the Active Directory database may become corrupted, or the virtual machine fails to start, and you may receive an error message that resembles the following:
c00002e2 Directory Services could not start because of the following error: %hs Error Status: 0x%x. Please shutdown this system and reboot into Directory Services Restore Mode, check the event log for more detailed information.
This issue occurs because the Hyper-V virtual IDE controller erroneously reports success if an operating system on the guest requests to disable the disk cache. This might result in an application issuing I/O operations that it believes are persisted to disk that are actually being allowed to reside in the disk cache, which would not be persisted across power failures of the Hyper-V host.
Go to the More information section for more background information.
Note After you install this update, requests to disable the disk cache in the Hyper-V virtual IDE controller will fail. This is the expected behavior. You may receive a warning message generated by Active Directory in the guest machine operating system. This event 1539 warning message states that "Active Directory Domain Services could not disable the software-based disk write cache on the following hard disk," followed by the drive letter of the hard disk. This warning message is generated when the Hyper-V virtual IDE controller correctly refuses the request to disable the disk cache. However, Active Directory requests all database updates be completed without caching, which the Hyper-V storage subsystem ensures in order to prevent data loss from a power failure or other unexpected reboot.
Windows Server 2012Install update rollup 2855336
(http://support.microsoft.com/kb/2855336/ )on the Windows Server 2012-based Hyper-V host.
Windows Server 2008 R2Install update 2853952 on the Windows Server 2008 R2-based Hyper-V host. Also, install update 2853952 on the guest if the guest is running Windows Server 2008 R2 or Windows 7.
This update is available from Windows Update and the Microsoft Download Center.
For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:
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119591Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.
(http://support.microsoft.com/kb/119591/ )How to obtain Microsoft support files from online services
Restart requirementA restart is required for the update to resolve this issue.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
There are various caching layers in the virtualization stack that affect consistency semantics of applications running on the virtual machines. For more information about this, refer to KB 2801713
Virtual hard disks report to a guest operating system that write-caching is enabled, and disks reject requests to disable write-caching that are made by the guest operating system. This behavior is necessary for the following reasons:
Before the update is installed, when Active Directory would try to disable the disk cache, Hyper-V would incorrectly report that this operation was successful. Then, Active Directory would perform file operations under the assumption that no caching was occurring, even though caching was occurring.
After you install this update, Active Directory will try to disable the disk cache, and Hyper-V will correctly report that this is not possible. Then, Active Directory will enable FUA (Force Unit Access) to make sure the data is not cached.
When Active Directory tries to disable the disk cache, event ID 1539
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/824684/ )Description of the standard terminology that is used to describe Microsoft software updates
Article ID: 2853952 - Last Review: September 30, 2013 - Revision: 6.0
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