title: how do you estimate RAM size for application server?
body: <p>I'm wondering what an appropriate way to estimate RAM
  size for application server is.</p>
  
  <p>I'm planning to build an application server with Apache as Web server and Django as application framework.
  databases exist on different nodes.</p>
  
  <p>at first, I thought finding out all cases that those middlewares use memory and 
  calculating how much each case would use memory would do the job.
  but now I'm lost on how to find those use cases and also wonder this is appropriate to find a suitable RAM size for this server.</p>
  
  <p>if anyone has experience on estimating RAM size for application server, could you tell me how you have done that or suggest me any book that would help me from this situation?</p>