Server sizing of Scale-out architecture

Hi,
I am planning ignition architecture and hardware sizing. We will have about 115,000 tags. Therefore, we planned to use scale-out architecture. I referenced the the article of Ignition Server Sizing and Architecture Guide_1, but the sizing guide is only for single server. Could anybody give some suggestions or reference about how to sizing the frontend server and I/O server for scale-out architecture?

Thanks ahead!