VSS Troubleshooting Guide – Failed VSS Writers

• Title

  VSS Troubleshooting Guide – Failed VSS Writers

• Description

  AppAssure 5 uses VSS as part of the recovery point creation process.
  If the VSS subsystem isn’t functioning properly, AppAssure will not be able to complete the backups.
  The following sections are designed to help remedy specific VSS issues that may occur within your system.
  Please note additional VSS troubleshooting details can be found in Microsoft’s TechNet article “Troubleshooting the Volume Shadow Copy Service.” Microsoft’s document provides additional troubleshooting steps that go beyond the scope of this article.
  

• Resolution

  Before moving on to the steps below, ensure that all service packs, hotfixes and and updates have been applied to the system.
  Should the problem still persist after applying all available service packs, hotfixes and and updates, please complete the following steps.
  

  1. Reboot your agent server. Servers that have not been rebooted in a while may cause VSS to malfunction. You should reboot your server regularly as a preventive and cleanup measure for your system.
     
     
  2. Reset the writers to a stable state.
     • Open vssadmin from the command line (run cmd prompt as administrator). Run the following command:
       • vssadmin list writers
     • If any writer is noted as failed or has an error, or any writers’ states are not listed as stable, run the following:
       • For Replay4: C:\Program Files (x86)\AppAssure Software\Replay Agent\Utils64 > vshadow <drive letter:>
       • For AppAssure 5, open a command prompt from the following location: C:\Program Files\apprecovery\agent
         • Run vShadow <drive letter:>
     • List the writers again to check their stability: vssadmin list writers
     • If there are still any writers that are listed as failed or have an error, please continue to the next step.
       
       
  3. Clear any existing shadows.
     • VSS has a limit on the number of snapshots that can be kept on the system; furthermore, these snapshots take up space on the drive that is needed to take these snapshots. The following will clear this space.
       
       
       • Open vssadmin from the command line (run cmd as administrator).
       • Enter vssadmin delete shadows /all
       • This will clean up the VSS snapshots. 
       • Some defective systems accumulate VSS snapshots that persist in the system.
       • Enter vssadmin list writers and check for errors.
       • If there are still any writers that are listed as Failed or have an error, or any writers’ states are not listed as Stable, please continue to the next step.
         
       • If you have recieved the following error:
         "Error: Snapshots were found, but they were outside of your allowed context. Try removing them with the backup application which created them."
         
         
         • Return to the elevated cmd prompt
         • Enter wmic
         • Enter shadowcopy delete
         • For each shadow copy it lists, enter Y
           
           
  4. Restart the services.
     • Open Services.msc and restart the following services:
       
       
       • COM+ Event System.
       • COM+ System Application Service. This may not be started (if not, start it).
       • Distributed Transaction Coordinator Service.
       • Volume Shadow Copy Service.
       • If possible please also restart the affected VSS writer service, for example Virtual Server 2005 VSS writer or the Hyper-V VM manager Service to the Hyper-V VSS writer.
         
         
     • Check the Event Viewer for any additional error information logged by that VSS writer.
     • Run vssadmin list writerst once more.
     • If there are any writers that are listed as failed or have an error, please continue to the next step.
       
       
  5. As noted above, VSS has a limit to the amount of space that is set to keep and take snapshots on occasion the default value 5% of the total size of the volume is not large enough. Please run the following command to set the size to have no limit.
     • vssadmin Resize ShadowStorage /For=<drive letter:> /On=<drive letter:> /MaxSize=UNBOUNDED
       Example:  vssadmin Resize ShadowStorage /For=C: /On=C: /MaxSize=UNBOUNDED
       
       
  6. On systems running a desktop operating system, the above command is the only way to set the size of the VSS Snapshot save location. On Windows Server Operating systems, the GUI can be used.
     • Open Disk Management: Click Start , click Run , type diskmgmt.msc and then click OK.
     • Right Click on the First Volume
     • Select Properties
     • Select the Shadow Copies Tab
     • Select The First Disk in the List
     • Select Settings
     • Select No Limit
     • Click OK
       
       
  7. If you don’t get any VSS writer errors when using vssadmin list writers, but the system isn’t able to create a new VSS snapshot (and you have deleted all existing snapshots), please continue to the next step.
     
     
  8. Uninstall all backup software on your computer, including Windows Backup if it is installed. You don’t need to uninstall Replay, because Replay doesn’t contain or install any VSS writers; however, we have seen VSS writers of other backup software manufacturers cause system instability and errors.
     
     
  9. After all other backup tools have been uninstalled, open the Registry Editor (regedit) as an administrator and check the following branch:
     
     HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\VSS\Providers
     
     
  10. After all other backup tools have been uninstalled, open Regedit as an administrator and check the following branch:
      
      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\VSS\Providers
      
      
  11. Underneath that key you should only find Microsoft Software Shadow Copy Provider. If you do find another, it may be a residual registry entry from a previous backup software installation. You can save the entry by exporting the entire registry to a file (right click and select Export) and then it’s safe to delete the entire branch entry underneath.
      
      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\VSS\Providers
      
      
  12. Reboot and run vssadmin list writers to confirm the problem has been resolved.
      
      WARNING:  Before making any changes to the registry, please export a copy of the registry to a memorable location so you can re-import it if necessary
      
      
  13. If the PC or server you are using is a virtual machine host, you need to install the latest VMware Tools (for VMware), Virtual Machine Additions (Virtual Server), and integration tools (Hyper-V) on each virtual machine.
      
      
  14. If you have completed all the above noted steps and you are still getting either VSS errors or unable to complete a snapshot, we recommend that you contact Microsoft Technical Support, as the issue is related to a malfunction within VSS or the Windows operating system.