You need to start by diagnosing the problem using some actual data. While I can assume SQL is the cause for you slowdown, this isn't necessarily true. Take a close look at your server logs and run some diagnostic tests that actually measure the slowdowns and provide you with a look at the programs that may be culprits.

SQL is often accused of causing problems that it did not cause. Sometimes it is bad database or query design. Sometimes it is lack of resources on the individual server. If the problem is SQL you may solve it by using a backend server or setting up load balancing.

In the interim examine all the variables and look at the appropriate diagnostic data to help with your troubleshooting.

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