Webstress testing

Hi,

  1. Please suggest a webstress open source tool that can run from a windows machine as well. We want to test if an online test application can handle 5000+ concurrent sessions.

  2. During this test, how can we monitor the performance of our Server? i.e. Web and DB both

Its a dedicated CentOS Server so resource is not an issue, the only thing is to make sure that it can take that much load.

Regards