One of the most common questions we get about LoadRunner Virtual Users relates to the resources required to execute the scripts on the Load Generator.  One advantage of the maturity of LoadRunner is that we have supported so many different drivers and protocols and environments over the past 2 decades.  We've learned so much about how to give a more detailed response to really advise users on how much Load Generator resources will be required to be successful.  You might imagine that the answer isn't black & white or even close to a 1 sentence answer.  Here are some simple ideas that can help you determine how to configure your Load Generators.

When it comes to calculating your virtual user footprint, it's actually quite easy.  But first, let me tell you that not everyone should need to do extensive calculations of the virtual user resource utilization.  This is important *only* when you have a very high number of virtual users or a very limited number of Load Generators.  The basic approach is to run a preliminary test with just 1 script, while you measure the resource utilization on the Load Generator directly.  You are specifically interested in the mmdrv.exe process on the Load Generator, which is LoadRunner's primary multi-threaded driver.  Measuring the private bytes reserved by this process for 1, 2, 3, 4 then 5 then 10 virtual users will give you some clue as to how much memory is required by each additional virtual user added.  Simultaneously you should monitor CPU, Network and Disk just to determine if there are any excessive utilizations.

It is important to note that you should be gathering information about the performance of your script running on the Load Generator - using the same run-time settings that you will use during the full scenario run.  If you are stress testing with very little think time or delay, then you'll want to use those same settings.