Re Register VSS Writers
“Re Register VSS” writers is the process that brings the unstable writers back to stable state. VSS writers are very important because they are used by backup applications to take the backup. For example, Microsoft Exchange has its own VSS Writer called “Microsoft Exchange Writer”. These writers should be in the “Stable ” state for the backups to be completed successfully.
We can check the status of the writers by running the following command on CMD:
VSSAdmin List Writers
The result looks like this:
Some times the writers become unstable or hang, as a result the backup fails. A simple server restart usually brings them back to the stable state as a result the backup starts working again. But some times the writers do not come back to the stable state. In those situations, we have to re register the volume shadow copy service Dll’s.
The method is same in Server 2008, 2008 R2, 2012, 2012 R2 and Server 2016. The steps are as follows:
First of all, open CMD and go to the “%WinDir%system32” directory
Secondly, run Net Stop VSS and Net Stop SWPRV to stop the volume shadow and MS Software shadow copy provider services.
Next run the following commands one by one to re register the dlls and services.
regsvr32 /s ole32.dll
regsvr32 /s oleaut32.dll
regsvr32 /s vss_ps.dll
regsvr32 /s /i swprv.dll
regsvr32 /s /i eventcls.dll
regsvr32 /s es.dll
regsvr32 /s stdprov.dll
regsvr32 /s vssui.dll
regsvr32 /s msxml.dll
regsvr32 /s msxml3.dll
regsvr32 /s msxml4.dll
Finally, run “Net Start SWPRV” and “Net Start VSS” to start the MS software shadow copy provider and volume shadow services.
Check the writers again by running “VSSAdmin List Writers”, and hopefully this time the writers will be in stable state and most importantly the backups will also complete.
For further reading, “Volume Shadow Copy Service”.