We can find a list with the compatible operating systems for FMPS13. If you want to use Webdirect, you will need to install Windonws Server 2008 R2 or Windows Server 2012. Using one machine, you will be able to use up to 6 concurrent connections (WebDirect). However, if you want to be able to have more then 6 concurrent connections, you will have to install a second machine with RAM, CPU and cores depending on the maximum concurrent connections. This second machine is called de "Worker machine" with the web publishing engine and webserver.
My question is : I suppose on the worker machine you will need to install Windows server 2008 or 2012. But, what operating systems should be installed on de first machine (The master machine) with the Database server on it???