Load Testing is designed to place an application under a load that is repeatable and scalable and that emulates a real world use case of the application. Setting up an environment (including test data) can be a time-consuming task, and one which is often done poorly.
The key words in the previous paragraph are 'repeatable' and 'scalable'. It is these two items, in conjunction with ensuring that the use case is relevant, which ensure that the performance is tested adequately.
There are many vendors and applications, that provide load test services and applications. However, as has been the goal throughout this book, I will use an actual example that you will be able to follow yourself. The example I will be using is Grinder, a popular open source load test framework that has been implemented handily into an Amazon AMI already for us.