On one Windows Server 2012 ist FileMaker Servers Database Engine on the second machine the Webpublishing Engine.
One thing i noticed is a performance issue when multiple php/xml requests are made.
Making https:// request is the most time slow (around 1000ms).
Making the same request with http is most time fast (around 20ms).
But not necessarily all the time...
It looks like that the spikes (slow response) from the https to the http request are opposite. When the https is slow, the http is fast, when the https is fast the https is slow. Most often, but not all the times.
I checked the times with the slow responses with the activity log in FileMaker Server. When a user makes a request with lots of data returned or an error 401 the response times drops for the next request.
This brings up the question: Can FileMaker Server request multiple (XML/PHP) at the same time, or does FileMaker Server process one request by one?