What is the minimum hardware to run Runbot efficiently?

I researched a lot for information about the hardware that is need to run Runbot efficiently in Odoo v8, for our software development team. Only I have found this link in which topic "1. REQUIRED RESOURCES" says as next:

  • At least 10 GB RAM, 50 GB HDD (100 GB preferred) and 4 cores (6-8 preferred)

What is recommended minimum hardware by Odoo developers to run efficiently Runbot?

If we're running Runbot for each 50-100 customers concurrently, what is your recommendation about hardware infrastructure?

Thanks a lot for any advises.