I'm part of a team moving dma's on to virtual infrastructure.  I was wondering if any one had come across any benchmarking / stress testing tools which give some truthful answers on machine performance.  Want to avoid the statement of it seems a bit slow / lagging

I know that there are some differences between a physical box and virtual machine but would like to test all we can for IO, RAM, CPU, Network

Where we are currently building and preloading with software would like to test them before we release for use.