Resolve issues with VSS errors on an Exchange server
Backups fail with errors pointing to VSS issues, and running the command ‘vssadmin list writers’ on your Exchange server lists your Exchange VSS writer as being in a failed state.
First, make sure no backup agents other than the Unitrends agent are installed on your server. If you’re using Server 2003, apply the hotfix listed in the “Third-Party Sources” section at the bottom of this article. Finally, re-register the .dll files by opening an elevated command prompt and running the following commands:
regsvr32.exe /i eventcls.dll
regsvr32.exe /i swprv.dll
Then reboot your server.
Server 2003 hotfix: http://support.microsoft.com/default.aspx?scid=kb;en-us;891957
This issue can have a number of root causes relating to the Exchange VSS writer on your server.
For more detailed information on backup failures and performance issues see Unitrends KB 5062 - Backup Failures and Performance Issues.