Benchmark is a free tool to measure the performance of a VMware virtualized infrastructure across three categories: efficient resource utilization, operational agility, and quality of service. Please visit labs.vmware.com/flings/vbenchmark to download the application.
vBenchmark directly queries existing vCenter Server data to provide a succinct set of metrics to help you measure and communicate configuration, activity and availability of your VMware virtualized private cloud. vBenchmark takes a snapshot of configurations, tasks and events from vCenter Server databases and returns a succinct set of metrics in each category. Snapshots are a quick and easy way to communicate key measures within your organization. As your private cloud evolves, measure changes over time by taking periodic snapshots and comparing your metrics. In addition, contribute your metrics to a community repository and in return, receive Peer Group benchmarks to see how your results compare.
--> The rest is to be seen on the blog : http://blogs.vmware.com/vsphere/2012/03/have-you-seen-vbenchmark-yet-free-tool-for-evaluating-your-virtualized-infrastructure-and-comparing-.html