Does anyone have a software tool or have a mathematical formula to predict/estimate Read/Write rates on a Lustre system?

I have a specific OSS design, a selected hard disk type, a specific MDS node design, and the size of the pipe between the compute nodes, MDS node and the OSS nodes. 

What other factors am I missing? RAID controller information? 

I am using CentOS 6.3 with Lustre 2.3.