If you are looking for performance reports then they are captured in the vCenter server itself. You cn use vSphere PowerCLI to write your own customized reporting tool.
Thanks,
Samir
P.S : If you think that the answer is helpful please consider rewarding points.
One of the best (free) ways to document a vSphere environment is to use the Virtualization EcoShell, which includes a way to generate reports and Visio diagrams. It is very easy to use and a great tool to keep in your toolbox for managing a VI3/vSphere environment.