General troubleshooting for Windows backup errors


General troubleshooting for Windows backup errors


This article discusses common troubleshooting steps for Windows backup errors.

For more detailed information on backup failures and performance issues see Backup Failures and Performance Issues


Troubleshooting Steps

  1. Review the Logs located in C:\PCBP\Catalog.dir and C:\PCBP\Logs.dir.
  2. Check the Event Logs (Application and System are common).
  3. Determine if any VSS writers have failed.
  4. Review the Task Scheduler for jobs that may be running when the Unitrends backup runs.
  5. Check that the schedules for SQL Maintenance and Exchange Maintenance plans do not conflict with the schedules for the Unitrends backup.
  6. You can not use our Application aware technology to backup a database that is being backed up by another backup program. If you must backup the database using another program (such as Microsoft a Maintenance), you can have us backup the file that it generates, but we will not be able to do an Application aware type backup.

 Reviewing the Logs: Review the following logs when troubleshooting Windows backup errors.
  1. Review the Unitrends Client Agent Logs for clues.
    1. Catalog.dir: Contains the logs for each backup performed. They are labeled according to the backup type. The sub-directory holds the logs for the Application based backups.
    2. Logs.dir: Contains the logs which pertain to the Agent operation and its communication to and from the Unitrends System. Typically, the first error listed in the yields the best.
  2. Review the Windows Application Event logs for the time which the backup began.
    1. The Unitrends agent software will log events throughout the course of the backup.
    2. The VSS snapshot is created shortly after the backup is started and will log events to the Windows Application Event log.
    3. Typically, the first error listed in the Windows Event log should be investigated first.
  3. Review the Windows System Event logs for the time which the backup began.
    1. The Unitrends agent service will log errors to the Windows System Event logs.
    2. Other services will also log to the Windows System Event log and present errors to investigate.

Verify the status of the VSS writers

1. VSS writers must be in a Stable state, and should show No Errors. If one has failed, you can try to correct it by rebooting the computer, using KB 4085, or by following Microsoft's best practice for restarting the affected VSS writer. Verify by using an Administrative Command Prompt and typing the following:

vssadmin list writers


2. When there are more than one VSS provider, a conflict in communication can occur. Verify this by using an Administrative Command Prompt and typing the following:

vssadmin list providers


The System Writer is usually the default on the OS and enumerates all operating system and driver binaries, which Unitrends to use for capturing critical System State information.

To prevent conflicts when more than one VSS Provider is found, edit the C:\PCBP\MASTER.INI file and add the following entry to the [usnap] section: UsnapProvider=System

The Change Journal and Servers with a lot of files or low resources or acting as an Active Directory Domain Controller

If you are backing up a server with a lot of files (such as a File Server), ensure the server has at least 4GB of RAM available at all times. This is because of how the Change Journal is handled during backups. By default only 500MB is reserved. However, larger servers or servers acting as an Active Directory Domain Controller may require this to be changed to reduce or eliminate the possibility of a journal wrap condition.

In the C:\PCBP\MASTER.INI file, look for the entry ChangeJournalSizeMB=500 and change the value to 1024. If you determine that more is needed, increment the value by 512.

WARNING:  This value is in MB and should at no cost exceed 4096 (4GB). The value chosen designates what RAM will be allocated for loading the Change Journal Data. Servers with low Memory can experience undesired behavior if it runs out of physical RAM. At the least, the backup will fail.


When backups are performed on a Windows system, Volume Shadow Copy Service (VSS) is used to capture open or locked files. Application-Aware backups are using with:

  • Microsoft SQL (2005 and up): SQL Full and differential backups are performed using VSS snapshots. Transaction log backups are performed using the Virtual Device Interface (VDI).
  • Microsoft Exchange (2003 and up) use snapshot technology.
  • Always verify your application or solution is supported using the Compatibility and Interoperability Matrix.

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