If you're trying to perform a peak load test, it's essential to understand the behavior of customers/real time users on the system. Consider how they ramp up their activities. Then, set your test ramp up time in a similar manner.

If the ramp up time is large, try to ramp up all users in a quarter of the time that it would usually take.

Image: A typical usage scenario showing ramp up and ramp down.

Specifying the correct ramp up time is essential when simulating a real time scenario.