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Thread: SQL Server Differential Backup fails

  1. #1

    Default SQL Server Differential Backup fails

    Windows Small Business Server 2003 R2, dual processor, 4 GB RAM
    SQL Server 2005, installed on C: drive
    Amanda Cloud Backup 3.0.2 installed on C: drive, which has 6 GB free space.

    vssadmin list writers shows all writer stable and no errors.
    amandabackup has role sa in the four SQL databases: MSSQLSERVER, SBSMONITORING, SHAREPOINT, and MICROSOFT##SSEE

    Full backup ran successfully last night at 23:00

    Differential backup failed this afternoon at 12:00, with error "MSSQL Log backup failed."

    The event log for today shows that "database differential changes were backed up" for databases msdb and model in MICROSOFT##SSEE. So far so good.

    Now, the first error, with event ID 18204: "BackupDiskFile::CreateMedia: Backup device C:\Program Files\Zmanda\misc\mssql_model_<serverName>_MICROSO FT##SSEE.TRN failed to create. Operating system error 5 (Access denied).

    In the last week since I have installed ZCB, I have run three full backup successfully, yet differential backup fails repeatedly. I don't understand why access is denied, nor how the log backup runs differently from the full backup.


  2. #2

    Default SQL Server Differential Backup fails

    I was just comparing the event logs for the successful Full Backup with the unsuccessful Differential Backup.
    For the Full Backup, the database backup all took place on behalf of the user NT AUTHORITY\SYSTEM.
    For the Differential Backup, user NT AUTHORITY\SYSTEM was successful backing up database differential changes. However, user amandabackup generated an error: Backup Disk File:: Create Media: Backup Device 'C:\Program Files\Zmanda\misc\mssql_model_<servername>_MICROSO FT##SSEE.TRN failed to create. Operating system error 5. Access is denied.

  3. #3
    Join Date
    Sep 2008


    The Windows Internal Database (MICROSOFT##SSEE) service creates a SQL
    instance MSSQL$MICROSOFT##SSEE which generally runs under the account "NT AUTHORITY\NetworkService".

    "NT AUTHORITY\NetworkService" account does not have the rights to write to
    folder "C:\Program Files\Zmanda\Zmanda Cloud Backup\misc\" or
    "C:\ProgramData\Zmanda\Zmanda Cloud Backup\misc\" (in case of Win 2008)

    Please check the account under which the MSSQL$MICROSOFT##SSEE instance is running and give write permissions to the ZCB installation folder to the account. In default case the account will be "NT AUTHORITY\NetworkService". This is the reason why log backups
    are failing as the MICROSOFT##SSEE service is trying to write to this folder
    during log backup as part of differential backup.

    Do let us know what happens.


  4. #4


    Good work Prashant! Thank you. I granted write permission to NETWORK SERVICE on the misc folder, and the differential backup succeeded.
    Is this something that should be in the setup guide?

  5. #5
    Join Date
    Sep 2008


    Hi Fred,
    I am glad the solution worked. Yes, I think this should go in the guide. I will update the documentation and it should be available in the next release.


  6. #6
    Join Date
    Feb 2011


    Good luck mediationworks. I believe that the solution of parshant is greatly useful. I think I'm gonna use it also.

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