I have 2 SQL Server 2008 instances installed on the same server. They have same table structures with same data. I have a stored procedure deployed on both of them. The stored procedure performs differently on them. It takes 5 seconds on one instance and 50 seconds on the other to execute the procedure. I think the possible reasons for this are: index fragmentation, outdated statistics. I defragmented the indexes and updated the statistics but still no luck. Any ideas on this issue?