Microsoft KB Archive/312067

= Shadow copies may be lost when you defragment a volume =

Article ID: 312067

Article Last Modified on 12/3/2007

-

APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition
 * Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
 * Microsoft Windows Small Business Server 2003 Standard Edition
 * Microsoft Windows Small Business Server 2003 Premium Edition

-



This article was previously published under Q312067



SYMPTOMS
When you run Disk Defragmenter on a volume with shadow copies activated, all or some of your shadow copies may be lost, starting with the oldest shadow copies.

After the shadow copies are lost, events that are similar to the following may be logged in the System log: Event Type: Warning

Event Source: VolSnap

Event Category: None

Event ID: 24 User: N/A

Computer: production

Description: There was insufficient disk space on volume C: to grow the shadow copy storage for shadow copies of C:. As a result of this failure all shadow copies of volume C: are at risk of being deleted.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

Data: 0000: 00000000 00580003 00000000 80060018 0010: 00000002 c000007f 0000003f 00000000 0020: 00000000 00000000 You may have several event ID 33 logged both before and after the event ID 24 is logged.

Event Type: Information

Event Source: VolSnap

Event Category: None

Event ID: 33 User: N/A

Computer: production

Description: The oldest shadow copy of volume C: was deleted to keep disk space usage for shadow copies of volume C: below the user defined limit.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

Data: 0000: 00000000 00580002 00000000 40060021 0010: 00000001 00000000 00000040 00000000 0020: 00000000 00000000



CAUSE
The System Shadow Copy provider uses a copy-on-write mechanism that operates at a 16-KB block level. This is independent of the file system's cluster allocation unit size. If the file system's cluster size is smaller than 16 KB, the System Shadow Copy provider cannot easily determine that disk defragmentation I/O is different from typical write I/O, and performs a copy-on-write operation. This might cause the Shadow Copy storage area to grow very quickly. If the storage area reaches its user-defined limit, the oldest shadow copies are deleted first.



RESOLUTION
If the file system's cluster size is 16 KB or larger, the provider can recognize disk defragmentation I/O and handle it correctly. Microsoft recommends that you use a 16-KB or larger cluster allocation unit size when you format the volume if you plan to defragment volumes that are used for shadow copies of shared folders,.



MORE INFORMATION
For more information about cluster allocation unit sizes, click the following article number to view the article in the Microsoft Knowledge Base:

140365 Default cluster size for FAT and NTFS

For additional information about best practices for using shadow copies of shared folders, see the &quot;Shadow Copies of Shared Folders: Best Practices&quot; topic in the Windows Server 2003 Help and Support Center.

Additional query words: defrag VSS 16K

Keywords: kbprb KB312067

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.