A failed SQL Server Service Pack upgrade is fixed with a trace flag.
Starting with SQL Server 2008 a new feature which allowed us to create compressed backup files by pre-allocating space. This tip will look at the performance impacts of disabling pre-allocation of space using the 3042 SQL Server trace flag.
The trace flag 8649 is incredibly useful. Alas, the flag is undocumented, unknown, and its full impact difficult to understand. Adam Machanic presents an alternative which you might find useful.