SQL VSS Writer is missing: databases will be backed up in crash-consistent state and transaction log processing will be skipped
Running the command vssadmin list writers shows that 'SqlServerWriter' is not active.
There are different causes of the issue:
the SQL instance has one or more databases with a name starting or ending in a space character.
the account under which SQL VSS Writer service is running doesn't have sysadmin role on a SQL server
SQL VSS Writer service stuck in an invalid state
This warning notifying that the "SQL VSS writer is missing" is a courtesy message that is presented to the user when Veeam Backup & Replication detects that the SQL VSS Writer is missing on a server where it was seen previously.
Below is a list of possible solutions that have been reported to us by customers from previous support cases.
Veeam is not responsible for any issues incurred after making the suggested changes. You are advised to contact and review all setting changes with the respective product support organization.
Reported causes\solutions to fix the SQL VSS Writer not be present on a SQL Server:
Use the "Repair" function within Apps & Features for the Microsoft VSS Writer for SQL Server
To check if your database has a space in the name you can run the following query on the SQL Server which has the missing SQL VSS Writer. If you notice any spaces in the database names, then you will need to remove the spaces from the database names. (Changing database names may require checking with the software that is using that database to make sure it can be changed to the new name.)
select'#'+ name +'#'from sys.databaseswhere name like'% %'
The # shown in the SQL query results makes it easier to spot leading and trailing spaces.
Make sure that the user specified in the [Log on as] for the SQL Server VSS Writer service is set as having a sysadmin role
Restart SQL Server VSS Writer service
In the case of SBS machines that are also Domain Controllers, ensure that the SQL Writer is running as a domain administrator and not local system
Allow the SQL Writer service account access to the Volume Shadow Copy service via the registry:
If the DWORD value “NT SERVICE\SQLWriter” is present in this key, it must be set to 1.
If the Volume Shadow Copy service is running, stop it after changing this registry value. Do not disable the Volume Shadow Copy service, it's default state is Manual.