Microsoft KB Archive/945058

= When you use the Volume Shadow Copy Service on Windows Server 2003-based computers that run many I/O operations, disk volumes take longer to go online =

Article ID: 945058

Article Last Modified on 12/27/2007

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APPLIES TO


 * Microsoft Windows Server 2003, Datacenter x64 Edition
 * Microsoft Windows Server 2003, Enterprise x64 Edition
 * Microsoft Windows Server 2003, Standard x64 Edition
 * Microsoft Windows Server 2003, Datacenter Edition for Itanium-Based Systems
 * Microsoft Windows Server 2003, Enterprise Edition for Itanium-based Systems
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
 * Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)

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Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 How to back up and restore the registry in Windows XP and Windows Vista



SYMPTOMS
When you use the Volume Shadow Copy Service on Windows Server 2003-based computers that run many I/O operations and that have lots of data, you experience the following symptoms:   Cluster failover time is longer for the cluster groups that contain disk resources for which you have enabled the Volume Shadow Copy Service. Also, the disk volumes of the cluster nodes take longer to go online and offline during a cluster failover. Taking a disk offline and then online on the same node also has the same delay.

The following events may be logged in the Application log: Event ID: 1035

Event Source: Clussvc

Description: Cluster disk resource 'Disk X:' could not be mounted. Event ID: 1069

Event Source: Clussvc

Description: Cluster disk resource 'Disk X:' failed.  Non-cluster servers take longer to start. When you disable the Volume Shadow Copy Service on the server volumes, the servers start as expected.



CAUSE
This issue occurs because of the way the Volume Shadow Copy driver (Volsnap.sys) manages the shadow copy files. If lots of shadow copy files are created on the disk volumes, the Volume Shadow Copy driver takes more time to process those shadow copy files when the system brings the disk volumes online.



WORKAROUND
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To work around this issue, create a new registry key to restrict the number of shadow copy files that are created on each disk volume to 20.

Note This value is only a suggested starting value. We recommend that you find a value that is appropriate for your working environment.

To create the new registry key, follow these steps:  Click Start, click Run, type regedit, and then press ENTER. Locate and then right-click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\Settings

 Point to New, and then click DWORD Value.</li> Type MaxShadowCopies, and then press ENTER.</li> Double-click MaxShadowCopies, type 20 in the Value data box, and then click OK.</li> Exit Registry Editor.</li> Restart the computer.</li></ol>

Additional query words: MSCS VSS Cluster failover long time Boot

Keywords: kbexpertiseinter kbtshoot KB945058

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