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Article ID: 925799 - Last Review: June 14, 2009 - Revision: 3.1

Important This article contains information about how to modify the registry. Make sure to 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:
256986  (http://support.microsoft.com/kb/256986/ ) Description of the Microsoft Windows registry

SYMPTOMS

When a Windows Server 2003-based computer has a high level of I/O activity, the following error message may be logged in the Application log:
Event Type: Error
Event Source: VolSnap
Event Category: None
Event ID: 25
Description: The shadow copies of volume Volume_Name were aborted because the diff area file could not grow in time. Consider reducing the IO load on this system to avoid this problem in the future.

CAUSE

This issue may occur when one or more of the following conditions are true:
  • The Volsnap.sys driver has encountered excessive I/O activity. Therefore, the "diff" area cannot grow.
  • The computer has run out of shadow copy storage space.

RESOLUTION

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 your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To resolve this issue, use one of the following methods:
  • Install Windows Server 2003 Service Pack 1 (SP1). For more information about how to obtain Windows Server 2003 SP1, click the following article number to view the article in the Microsoft Knowledge Base:
    889100  (http://support.microsoft.com/kb/889100/ ) How to obtain the latest service pack for Windows Server 2003
  • When the cause is insufficient shadow copy storage space, double the storage space allocation.
  • Use a second hard disk exclusively for shadow copy storage.
  • Increase the free disk space that is available on the volume that is used.
  • Create the following registry subkey to adjust the diff area size:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VolSnap\MinDiffAreaFileSize
    To do this, follow these steps:
    1. Click Start, click Run, type regedit, and then click OK.
    2. Locate and then click the following registry subkey:
      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VolSnap
    3. On the Edit menu, point to New, and then click DWORD value.
    4. Type MinDiffAreaFileSize, and then press ENTER.
    5. On the Edit menu, click Modify.
    6. Compute a value that is five percent of the smallest shadow copy storage space on any one volume on the system.
    7. Use the following guidelines to set the MinDiffAreaFileSize value:
      • If you compute a value that is less than or equal to (<=) 600 megabytes (MB), set the MinDiffAreaFileSize value to 600. If you continue to receive event ID 25, incrementally increase the value until the value exceeds 3,000.
      • If you compute a value that is more than or equal to (>=) 3,000 MB, set the MinDiffAreaFileSize value to 3000.
      • If you compute a value that is between 600 MB and 3,000 MB, set the value of MinDiffAreaFileSize to the value that you computed.
    Note Shadow copies may not function correctly if the value of the MinDiffAreaFileSize registry subkey is larger than the maximum size of the shadow copy storage area. For example, if you set the registry setting to 1024 MB, backup software will not generate snapshots of the 200 MB system partition. Therefore, before you create the MinDiffAreaFileSize registry subkey, make sure that the diff area file is larger than 300 MB or that the diff area file is larger than the value that is specified in the registry. Also, make sure that you have at least 300 MB of free space on the shadow copy storage volume.
If you continue to receive event ID 25, follow these steps to resolve the issue:
  1. Put the shadow copy storage on another volume, even if the volume is located on the same hard disk.
  2. Make sure that the volume that causes event ID 25 is not the same volume that contains the paging file. If the volume that causes event ID 25 contains the paging file, consider putting the paging file on another volume.
  3. Make sure that the volume that causes event ID 25 is not used as the shadow copy storage for any other volume.

APPLIES TO
  • Microsoft Windows Server 2003, Standard Edition (32-bit x86)
  • Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
  • Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
  • Microsoft Windows Server 2003, Web Edition
  • Microsoft Windows Server 2003, Datacenter Edition for Itanium-Based Systems
  • Microsoft Windows Server 2003, Enterprise Edition for Itanium-based Systems
Keywords: 
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