I have worked on a very huge database system that does not have proper indexing. (SQL Server 2008 Standard). After putting indexes in place, I see that the Avg Disk Queue length reduced to 6 from 16 which is more than 200% improvement. However, avg cpu is down only by 13% from 65% to 52%. I have run perfmon traces for 2 days before and after the changes to note these values. There are no changes done to code (still the same bad coding)
I want to understand why cpu usage did not reduce to a large extent, any thoughts?