Backup & Recovery uses the Microsoft Volume Shadow-Copy Service to take a snapshot of the databases. In order for this to be successful, the following statements must be true.
- Microsoft Volume Shadow-Copy Service service running and stable.
- SQL Server VSS Writer service running and the writer in a stable state. To check if this is the case, run the vssadmin list writers command from the command line:
Backup & Recovery does not truncate the MS SQL logs as the MS SQL VSS writer used for the backup does not support this functionality, however iIf the database uses the Simple Recovery mode, its logs are truncated automatically by the MS SQL server when the database reaches a transaction checkpoint.
Potential causes of failure
In the unlikely event that the initial backup of a large database takes longer than 24 hours to complete, the backup scheduled for the following day will be skipped with the message "Running a second simultaneous backup of VSS-based plugin is not allowed". This will show as "NotStarted" in Dashboard.
Depending on the configuration of SQL Server, there may not be sufficient threads available to create a snapshots of multiple databases simultaneously. This could result in a failed session with VSS error 0x800423f4. Microsoft has an article for the issue and workaround for it:
If you are running a 64-bit version of SQL Server, you can consider increasing the Max Worker Threads configuration option.
If you are running a 32-bit version of SQL Server, please check the influence of increasing of Max Worker Threads to performance.
Also, as described in the following Microsoft article, a VSS backup may fail for some databases if the database name contains either leading or trailing spaces or non-printable characters.
We are not responsible for the content of external sites.