Microsoft's Volume Shadow Copy is probably amongst the most complex functions of the Windows operating system; hence, if it breaks it is a time consuming process to repair.

Symptoms of a Volume Shadow Copy Malfunction

• Very long (or seemingly indefinite) VSS snapshot generation time with intensive hard drive activity.
• VSS errors reported in the Event Viewer (click start and search Event Viewer in search box to open)
• VSS errors reported by Microsoft's Volume Shadow Copy tool vssadmin
• VSS fails to create snapshots.

Contents:

Most Common

• VSS Repair Strategy #1 - Available Disk Space and Reboot
• VSS Repair Strategy #2 - System File Check
• VSS Repair Strategy #3 - VSS shadows
• VSS Repair Strategy #4 - VSS Command Line Troubleshooting

More Advanced Configurations

• VSS Repair Strategy #5 - Complete Uninstall and Reinstall of all backup software
• VSS Repair Strategy #6 - Virtual machines
• VSS Repair Strategy #7 - COM Subscription corruption
• VSS Repair Strategy #8 - Windows Update
• VSS Repair Strategy #9 - Additional Non-Microsoft VSS Provider(s)

Most Common

Please complete these strategies in order, until the problem is resolved.

VSS Repair Strategy #1 - Available Disk Space and Reboot

1. Check your free disk space on ALL volumes/partitions on the PC where NovaBACKUP is installed. If disk space is too low, VSS will cause the backups to fail if "Open File Backup" is enabled, which it is by default in NovaBACKUP. VSS utilizes disk space on your partitions, not just the C: drive, to cache data. VSS alone can utilize the remaining disk space on your partition and you would not even know it unless you knew about the command line functions to check that disk space usage for VSS.
2. Reboot. For some reason, servers that haven't been rebooted in a while can cause VSS to malfunction. As all Microsoft veterans know, you need to reboot regularly as a preventive and cleanup measure for your system.

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VSS Repair Strategy #2 - System File Check

Run the System File Checker (SFC) with these steps:

1. Click the Start orb and then type cmd in the Search programs and files field.
2. In the results area, right-click cmd.exe, and then click Run as administrator. You will be prompted to type the password for an administrator account. Click Continue if you are the administrator or type the administrator password. Then, click Continue.
3. At the command prompt, type SFC /scannow, then press ENTER. This will scan the system files and configuration on your machine.

The scan may take some time, so be patient. Windows will repair any corrupted or missing files that it finds

If you receive a message that SFC was unable to repair corrupted files, you can try using the Deployment Image Service and Management (DISM) tool to repair issues:

1. Click the Start orb and then type cmd in the Search programs and files field.
2. In the results area, right-click cmd.exe, and then click Run as administrator. You will be prompted to type the password for an administrator account. Click Continue if you are the administrator or type the administrator password. Then, click Continue.
3. At the command prompt, type DISM /Online /Cleanup-Image /RestoreHealth, then press ENTER. This will pull files from the online Windows Repository to your machine.
4. Run SFC /scannow again after this completes.

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VSS Repair Strategy #3 - VSS shadows

Open vssadmin from the command line (run cmd as administrator).

Enter vssadmin delete shadows /all to clean up any dead VSS snapshots. Some defect systems accumulate hundreds of VSS snapshots that persist in the system and cause Windows to become unresponsive.

If vssadmin delete shadows /all is unable to remove all shadows, try this:

vssadmin Resize ShadowStorage /For=C: /On=C: /MaxSize=300MB

For each drive, run the above command with the minimum MaxSize permitted (300MB). Windows will then voluntarily dump all shadows due to lack of space for the shadow copies. 

Then, set MaxSize to UNBOUNDED or a very high number (for example, 100GB) for good performance. This is just an upper limit, not an actual permanent storage allocation. This needs to be 50GB or 10% of the drive (whichever is higher).

There is an alternate method for Server Operating Systems if vssadmin /delete shadows all does not work, or encounters errors: use DISKSHADOW from administrative cmd prompt.

1. diskshadow [enter]
2. delete shadows all [enter]

Enter vssadmin list writers and check for errors. If you receive any errors for one VSS writer, you may need to fix that particular VSS writer. It is common to receive writer errors caused by Microsoft's Virtual Server 2005 VSS writer.

How To Resolve VSS Writer Errors Without Rebooting

Check the Event Viewer for any additional error information logged by that VSS writer.

Run again vssadmin list writers to check if the above resolved the problem.

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VSS Repair Strategy #4 - VSS Command Line Repairs

You can try to re-register all VSS and COM components by following our FAQ on VSS Command Line Repairs

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More Advanced Configurations

Writer Class Id: {e8132975-6f93-4464-a53e-1050253ae220}
Writer Name: System Writer
Writer Instance ID: {34162f4c-59ff-468e-848d-cb4b3d8dd7dc}

Provider name: 'Symantec Software VSS Provider'
 Provider type: Software
 Provider Id: {262b716e-bb23-41b5-aaef-e2c15e767167}
 Version: 1.0

Volume Shadow Copy Service error: A critical component required by the Volume Shadow Copy service is not registered. This might happened if an error occurred during Windows setup or during installation of a Shadow Copy provider. The error returned from CoCreateInstance on class with CLSID {790f2886-9889-4c99-8ef5-531add05d044} and Name SW_PROV is [0x80040154, Class not registered
]. 

Operation:
 Obtain a callable interface for this provider
 List interfaces for all providers supporting this context
 Check If Volume Is Supported by Provider

Context:
 Provider ID: {262b716e-bb23-41b5-aaef-e2c15e767167}
 Class ID: {790f2886-9889-4c99-8ef5-531add05d044}
 Snapshot Context: 0
 Snapshot Context: 0
 Execution Context: Coordinator
 Provider ID: {00000000-0000-0000-0000-000000000000}
 Volume Name: \\?\Volume{ec87cfc6-061c-11e1-97aa-806e6f6e6963}\