Increasing VUsers does not increase hits per second

Hi all,

I just ran a load test to an external website against one of our partners, and we were attempting to perform capacity testing. Our requests were all GET requests.

We started the load test with 100 VUsers. Our partners reported a hits/second value of 600. We configured the VUsers to start a request immediately after the last call finished. We then increased the VUsers to 200. Our partners reported hits/second up near 1200, as expected. However, when we then increased Vusers to 400, there was no noticeable increase from our partners regarding traffic. The hits/second stayed around 1200.

We verified that we were nowhere near our outbound internet connection bandwidth. Our load generating server has 8GB of ram and we were only using 1, our processor usage was hovering around 30% on a dual processor dual-core machine (4 cores total). We also noticed that errors were not increasing, and the avg response time stayed consistent. We have a license that allows 1000 VUsers, and have used all 1000 Vusers in load tests against internal applications.

I believe it's a configuration issue within Load Runner. If it was a network issue, we would have seen requests queue up and thus the response times to increase, right?

Thanks, your help is appreciated.