Any known rules for max vhosts for apache? Tools?

[Peter Holm <listbot@gmx.de>]

Hi,

are there any rules for calculating the max vhosts / cpu / memory
needed for x domains? 

i want to know, how i can estimate how many vhosts I can put on a
server and how to calculate this.

Of course, i know that this depends on traffic / load etc. 

Only thing I have for know are logfiles for some months, so I could
calculate something based on these logs. 

Is there a reliable way to calculate the amount of needed ram based on
logfiles? I think RAM is the limiting factor. 

I could imagine that I am not the first one with these thoughts, maybe
someone can point me to a project? 

Any recommendations, pointers or experiences are welcome ;)

Thank you very much for your attention.

Peter