Symptoms

On a computer that is running Windows Server 2008, you use the Hyper-V Volume Shadow Copy Service (VSS) writer to back up virtual machines concurrently. However, the virtual machine backup operation fails. When this issue occurs, the following events are logged in the event log:

Event 1Event 2Event 3

Cause

The VSS service performs a snapshot cleanup operation during the VSS service startup and the snapshot deletion process. The snapshot cleanup operation deletes aborted snapshots and cleans up other snapshots (such as finds read/write snapshots, and then changes them to read-only snapshots). However, when the snapshot deletion process occurs the cleanup operation may create a race condition that may interfere with the snapshot creation process. In the race condition, the cleanup operation may mark the snapshot as read-only during an auto-recovery process. This behavior causes Hyper-V VSS writer not to auto-recover the snapshot successfully. Therefore, the Hyper-V VSS writer fails in the backup operation.

Resolution

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem is that described in this article. Apply this hotfix only to systems that are experiencing the problem is described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


Important Windows Vista and Windows Server 2008 hotfixes are included in the same packages. However, only one of these products may be listed on the “Hotfix Request” page. To request the hotfix package that applies to both Windows Vista and Windows Server 2008, just select the product that is listed on the page.

Prerequisites

To apply this hotfix, your computer must be running one of the following operating systems:

  • Windows Server 2008

  • Windows Server 2008 Service Pack 2 (SP2)

Restart requirement

You must restart the computer after you apply this hotfix.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.


For all supported x86-based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Swprv.dll

6.0.6001.22434

311,808

15-May-2009

13:02

x86

Swprv.dll

6.0.6002.22137

311,808

15-May-2009

12:52

x86

For all supported x64-based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Swprv.dll

6.0.6001.22434

481,280

15-May-2009

13:18

x64

Swprv.dll

6.0.6002.22137

481,280

15-May-2009

12:51

x64

For all supported Itanium-based versions of Windows Server 2008

File name

File version

File size

Date

Time

Platform

Swprv.dll

6.0.6001.22434

835,584

15-May-2009

12:54

IA-64

Swprv.dll

6.0.6002.22137

835,584

15-May-2009

12:44

IA-64

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates


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