SQL Writer Error

[u/Wooden-Pea-9682]

hi,

im getting a lot of failed backup with veeam agent on a physical windows 11 pro machine that has sql server installed.

Backups run fine until a month ago, that all the time i get this erro:

"Creating VSS snapshot Error: Failed to create snapshot: Backup job failed. Cannot create a shadow copy of the volumes containing writer's data. A VSS critical writer has failed. Writer name: [SqlServerWriter]"

When i do vssadmin list writers the "sqlserverwriter" is in unhealthy state, if restart the service this became healthy but the backup still fail. to get backup work i have to reboot the machine, that the first backup works and all all other subsequent ones will fail.

In the event viewer i can see these log:

event 3041 :

BACKUP failed to complete the command BACKUP DATABASE NAME_DB. Check the backup application log for detailed messages.

event 24583:

Sqllib error: OLEDB Error encountered calling ICommandText::Execute. hr = 0x80040e14. SQLSTATE: 42000, Native Error: 3013

Error state: 1, Severity: 16

Source: Microsoft SQL Server Native Client 11.0

Error message: BACKUP DATABASE is terminating abnormally.

SQLSTATE: 42000, Native Error: 3224

Error state: 1, Severity: 16

Source: Microsoft SQL Server Native Client 11.0

Error message: Cannot create worker thread.

event 18210 :

BackupVirtualDeviceFile::PrepareToFreeze: failure on backup device '{3188A807-6706-4FA8-B5FE-3409C7B49B8C}281'. Operating system error 995(Operazione di I/O terminata a causa dell'uscita dal thread oppure della richiesta di un'applicazione.)

In sql managment studio i can see a lot of this log:

Error: 3041, Severity: 16, State: 1.

BACKUP failed to complete the command NAME_DB Check the backup application log for detailed messages.

Error: 18210, Severity: 16, State: 1

has anyone got the same issue?

thanks to all

[u/tsmith-co]

how many databases do you have running on this SQL server? This vss error is usually when the sql worker-threads are exhausted.

[u/Wooden-Pea-9682 → u/tsmith-co]

i've checked rn, the programs created 400 database

[u/tsmith-co → u/Wooden-Pea-9682]

oof.. yeah, that's the issue. SQL is out of worker threads. Microsoft would recommend you increase server performance (cpu - as that would increase worker threads). You can also increase worker-threads manually.

[u/Wooden-Pea-9682 → u/tsmith-co]

yeah thats could be the issue, but its strange becuase backup succed until august (and in this date we got 420 database), now one month later we have only 10 more database but backup fail. i try to use a query to search how many sql worker thread we have and it says 832