Cannot start shadow copy (VSS_E_WRITERERROR_NONRETRYABLE) (MS SQL server with large number of databases)
Article ID
Product Version
Operating System
Symptom
When performing either a scheduled or manual MS SQL database backup job, where there are a large number of databases selected in the backup source. The following backup error is received in the backup report:
| No. | Type | Timestamp | Log |
|---|---|---|---|
| * | ... | ... | ... |
| * | info | ... | [Start]Backing up database... |
| * | erro | YYYY/MM/DD hh:mm:ss | Cannot start shadow copy, reason =The writer operation failed because of an error that might recur if another shadow copy is created. (VSS_E_WRITERERROR_NONRETRYABLE) |
| * | ... | ... | ... |
Cause
The error message is returned by MS SQL VSS writer, suggesting that there was an insufficient number of worker threads configured on the MS SQL Server to support the backup of all databases selected for backup.
A MS SQL Server databases backup job using VSS requires three worker threads per database. For example, a 64 bit MS SQL server with 4 CPUs is automatically configured with 512 work threads, which implies that the maximum number of databases that can be selected for backup is 170.
Please refer to the Limitations and Restrictions section in the following article for more details:
Resolution
To resolve this issue, either:
Option 1
Create additional backup sets (to be performed at different times) for the excess databases.
or
Option 2
Increase the maximum number of worker threads on the MS SQL Server.
To configure the max worker threads option:
- In the Object Explorer, right click a server and select Properties.
- Click the Processors node.
- In the Max worker threads box, type or select a value for the max worker thread.
For more details, refer to the following article: Configure the max worker threads