Microsoft KB Archive/940041

= Volume Shadow Copy Service snapshots may be unexpectedly deleted after you restart a Windows Server 2003-based computer =

Article ID: 940041

Article Last Modified on 10/11/2007

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APPLIES TO


 * Microsoft Windows Server 2003, 64-Bit Datacenter Edition
 * Microsoft Windows Server 2003, 64-Bit Enterprise Edition
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
 * Microsoft Windows Server 2003, Datacenter Edition for Itanium-Based Systems
 * Microsoft Windows Server 2003, Datacenter x64 Edition
 * Microsoft Windows Server 2003, Enterprise Edition
 * Microsoft Windows Server 2003, Enterprise Edition for Itanium-based Systems
 * Microsoft Windows Server 2003, Enterprise x64 Edition
 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Standard x64 Edition
 * Microsoft Windows Server 2003, Web Edition

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SYMPTOMS
After you restart a Windows Server 2003-based computer, Volume Shadow Copy Service (VSS) snapshots may be unexpectedly deleted.

This problem affects System Center Data Protection Manager (DPM) because DPM relies on volume snapshots to maintain its recovery points. Because the volume snapshots are unexpectedly deleted after Windows Server 2003 is restarted, DPM cannot list any recovery points.

This problem can also affect other third-party backup applications that rely on volume snapshots for their backup solutions.



CAUSE
The snapshots may be lost when the copy-on-write activity that is required to maintain the snapshots fails. This behavior may occur if one or more of the following conditions are true:
 * The live volume comes online more than five minutes before the difference (diff) area volume comes online.

Note The live volume is the volume from which the snapshots are made.
 * The diff area is inaccessible.
 * The grow request of the diff area is not handled on time.
 * The space of the diff area volume is insufficient.



RESOLUTION
A hotfix is available to resolve this problem. This hotfix introduces a new mode that is called Snapshot Protection mode. This mode blocks all I/O activities to the live volume when the diff area is unavailable for any reason. Therefore, snapshots are not deleted if the copy-on-write activity to the diff area fails.

By default, Snapshot Protection mode is turned off. You can enable this mode by using the public interfaces that are exposed by VSS.

Hotfix information
A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows Server 2003 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites
To apply the hotfix, you must have one of the following service packs installed on the computer:
 * Windows Server 2003 Service Pack 1 (SP1)
 * Windows Server 2003 Service Pack 2 (SP2)

Restart requirement
You have to restart the computer after you apply this hotfix.

Hotfix replacement information
This hotfix does not replace any other previously released hotfixes.

Registry information
To use one of the hotfixes in this package, you do not have to make any changes to the registry.

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.

Windows Server 2003 with SP2, Itanium-based versions


STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
After you apply the hotfix, an application can set the live volume or the diff volume to Snapshot Protection mode by using the SetVolumeProtectLevel function of the VssDifferentialSoftwareSnapshotMgmt3 object. Then, the SetVolumeProtectLevel function will call the IOCTL_VOLSNAP_SET_SNAPSHOT_PROTECTION_MODE input and output control (IOCTL).

You must also set the diff area volume to Snapshot Protection mode. If the live volume is lost, the diff area may be deleted when the Volsnap.sys driver performs the garbage collection.

In Snapshot Protection mode, the Volsnap.sys driver prevents read operations and write operations from accessing a volume at the first instance of any failure that may cause a loss of snapshots. When this instance occurs, the Volsnap.sys driver posts an event to indicate the reason for the failure. This event also indicates that the Volsnap.sys driver is blocking all I/O activities to the volume.

To return to Normal mode from Snapshot Protection mode, the application calls the SetVolumeProtectLevel function. Then, the SetVolumeProtectLevel function calls the IOCTL_VOLSNAP_RESET_SNAPSHOT_PROTECTION_MODE IOCTL.

