As I said earlier...
GilaMonster (7/15/2013)
If SQL cannot open and recover master and model successfully, SQL's startup process will fail. If MSDB can't be opened and recovered, SQL Agent will not be able to run.
Open and recover = open database, run crash recovery.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability