Hi,

I have the same problem, where the instance will not start after a service pack upgrade.

If I go to the alertlog file, I see this:

2014-12-02 10:53:47.93 spid7s MODIFY FILE failed. File 'MSDBLog' does not exist.

2014-12-02 10:53:47.94 spid7s Error: 912, Severity: 21, State: 2.

2014-12-02 10:53:47.94 spid7s Script level upgrade for database 'master' failed because upgrade step 'sqlagent100_msdb_upgrade.sql' encountered error 598, state 1, severity 25. This is a serious error condition which might interfere with regular operation and the database will be taken offline. If the error happened during upgrade of the 'master' database, it will prevent the entire SQL Server instance from starting. Examine the previous errorlog entries for errors, take the appropriate corrective actions and re-start the database so that the script upgrade steps run to completion.

2014-12-02 10:53:47.94 spid7s Error: 3417, Severity: 21, State: 3.

2014-12-02 10:53:47.94 spid7s Cannot recover the master database. SQL Server is unable to run. Restore master from a full backup, repair it, or rebuild it. For more information about how to rebuild the master database, see SQL Server Books Online.

These are my registry settings:

HKHKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL10_50.I2008\Setup\SQLDataRoot

F:\Program Files\Microsoft SQL Server\MSSQL10_50.I2008\MSSQL

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL10_50.I2008\MSSQLServer\DefaultData

K:\MSSQL.1\MSSQL\Data

As per http://blogs.msdn.com/b/sqlserverfaq/archive/2010/10/27/sql-server-2008-service-fails-to-start-after-applying-service-pack-1.aspx I tried to change the latter path to

F:\Program Files\Microsoft SQL Server\MSSQL10_50.I2008\MSSQL

and I tried

F:\Program Files\Microsoft SQL Server\MSSQL10_50.I2008\MSSQL\Data

, but that does nothing.

On the folder with the MSDB database, these are the permissions:

SYSTEM: Full controll

SQLServerMSSSQLUser$<servername>$<instancename>: Full control

Administrators: Full control

I tried adding the service account that rns the SQL Server instance, but that that didn't work as well. Also, there is enough space on al harddrives. What should i do?