loadUI is my suggestion as an open source Load Testing
solution that is free and cross-platform. Very useful to test our servers deployed with Interworx, whatever alone or clustered.
“With a visual, drag-and-drop interface, it allows you to create, configure and redistribute your Load Tests interactively and in real-time. In a single test environment, loadUI provides complete test coverage and supports all the standard protocols and technologies. And it?s so powerful, it generates scalable, high-volume and real-world load from any number of local and remote computers. Meet loadUI, the future of Load Testing”.