Same tables with same data, different SQL Server stored procedure performance 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 I think the possible reasons for this are: index fragmentation, outdated statistics.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?

Thanks
Are the two instances indentically configured?

One thing to check is if the instances have the same memory allocation.