Time-out errors occur in Volume Shadow Copy service writers, and shadow copies are lost during backup and during times when there are high levels of input/output

Time-out errors occur in Volume Shadow Copy service writers

Sometimes, during the backup process, some Volume Shadow Copy service writers might fail because of time-out errors that cause the backup to fail. A Volume Shadow Copy service writer is a program or a service that uses Volume Shadow Copy service to save information to a shadow copy storage area. For example, when you use the NTBackup program, the backup may not be successful, and you may receive the following error message:

To diagnose the Volume Shadow Copy service writer problem, run the vssadmin command immediately after the backup failure:

1. Click Start, and then click
   Run.

2. Type vssadmin list writers.

This command lists the Volume Shadow Copy service writers and the current state of each writer. For example, the output might indicate that the Microsoft SQL Server Desktop Engine (MSDE) or the Microsoft Active Directory directory service writer failed. You may experience time-out errors on several writers, including the MSDE writer, the SQL writer, the New Technology Directory Service (NTDS) writer, the Windows Internet naming system (WINS) writer, the Dynamic Host Configuration Protocol (DHCP) writer, the Remote Storage writer, the certification authority writer, and the Microsoft Exchange writer. The following is sample output:

Additionally, certain time-out errors can be identified by looking in the application event log. Some examples:

Shadow copies are lost during backup and during times when there are high levels of input/output

Another related symptom is that shadow copies of shared network folders may have been deleted. When this problem occurs, the following event error is logged:

In the message, VolumeName is the name of the volume that is scheduled for backup.

Volume Shadow Copy service writer time-out

You may experience a problem that causes certain Volume Shadow Copy service writers to time out during a lengthy shadow copy creation. This problem occurs especially on computers that have slow hard disks, low memory, or low CPU speed; or on computers that have the disk write cache disabled (for example, on a domain controller computer).

Shadow copy creation includes a complex sequence of inter-process calls. The inter-process calls make sure that all the important Volume Shadow Copy service writers (programs such as SQL, Exchange Server, operating system services, and others) flush their data buffers during shadow copy creation. Also, some Volume Shadow Copy service writers, like the Exchange writer, wait to write for a predefined time interval so the shadow copy can be created during the time interval. The writers wait to write so the contents of the shadow copy will be consistent with their data buffers. However, if there is low CPU speed, high memory usage, or high input/output levels, you may experience the following behaviors:

• The writers do not flush their data buffers.

• The writers do not wait the time interval before they write.

When this problem occurs, shadow copy creation fails.

Important Volume Shadow Copy service writers may fail with similar errors because of other conditions. These conditions include a lack of disk space or improper configuration of the computer. This hotfix addresses only the specific timeout errors that might randomly occur in Volume Shadow Copy service writers during backup. You are strongly advised to review the event log for any other potential Volume Shadow Copy service errors that might generate a writer failure.

Shadow copy deletion

You may also experience a problem in the Volsnap.sys driver that causes shadow copy deletion when there is a high level of input/output, especially when the disk write cache is disabled (for example, on a domain controller computer).

By default, the shadow copy provider that is included in Microsoft Windows Server 2003 is used to create shadow copies for backup purposes. The shadow copies are implemented by using a copy-on-write implementation. The differences are also copied in the shadow copy storage area. In Volume Shadow Copy service, you can use the shadow copy management tool, or you can use the vssadmin command.

In the original released version of Windows Server 2003, the initial shadow copy storage area that is allocated for shadow copy creation is 100 megabytes (MB). However, the actual space that is used is much smaller. As time passes, the allocated space may increase as more data is modified on the original volume. However, when you have high input/output traffic on the original volume, the shadow copy storage area cannot grow fast enough to hold all the copy-on-write changes. This causes deletion of all the shadow copies on the original volume. This problem is more noticeable in domain controller configurations. By default, the disk write cache is disabled in domain controller configurations.

Important A similar problem is caused by defragmenting a volume with small cluster size, where all shadow copies are deleted, and where the event log error that is listed earlier in this article is logged. For additional information about losing shadow copies during a disk defragmentation, click the following article number to view the article in the Microsoft Knowledge Base:

312067 Shadow copies may be lost when you defragment a volume

Also, event error ID 2004 may be logged when there are corrupted NTFS file system volumes. To determine if this is the problem, run the Chkdsk.exe program with the /f switch.

Large audit log

Writer time-out errors might also appear during a system-state backup if the audit log is extremely large. It is best to back up or to clean the audit log periodically.

Hotfix information

To resolve this problem, obtain the latest service pack for Windows Server 2003. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

889100 How to obtain the latest service pack for Windows Server 2003
A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. 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.

Date         Time   Version      Size       File name
-------------------------------------------------------------
28-Aug-2003  19:37  5.2.3790.81  1,054,720  Esent.dll        
28-Aug-2003  18:51  5.2.3790.81    271,360  Swprv.dll        
28-Aug-2003  18:51  5.2.3790.81    116,736  Volsnap.sys
28-Aug-2003  18:51  5.2.3790.81    642,560  Vssvc.exe        
12-Aug-2003  18:54                     271  Branches.inf
28-Aug-2003  19:50                  10,886  Kb826936.cat
28-Aug-2003  19:39                     354  Updatebr.inf
28-Aug-2003  19:39                   5,697  Update_rtmqfe.inf

Date         Time   Version       Size       File name         Platform
-----------------------------------------------------------------------
28-Aug-2003  19:33  5.2.3790.80   2,604,544  Esent.dll         IA-64
28-Aug-2003  19:33  5.2.3790.80     698,368  Swprv.dll         IA-64
28-Aug-2003  18:51  5.2.3790.80     347,136  Volsnap.sys
28-Aug-2003  18:51  5.2.3790.80   1,751,040  Vssvc.exe         IA-64
12-Aug-2003  18:54                      271  Branches.inf
28-Aug-2003  19:49                   10,886  Kb826936.cat
28-Aug-2003  19:40                      354  Updatebr.inf
28-Aug-2003  19:40                    5,717  Update_rtmqfe.inf