I Want to Know if Servers Can Handle Pressure

The Response Times Versus Load graph (ANALYZE > Graphs > Statistics > Response Time Versus Load) can help you uncover otherwise hidden scaling problems.

If response times increase to a non-acceptable level when the number of requests per second increases, it's very likely the result of an overloaded server getting more requests than it can handle.

In the example (click thumbnail to view image in full size), the gray server responds quickly no matter how many requests it gets. However, the response times (horizontal axis) of the purple server dramatically increase when the server gets many requests (vertical axis)—a typical sign of an overloaded server that could benefit from a hardware upgrade in order to perform better at busy times.