title: Elasticsearch - Why is it recommended to use 50% of available memory for the heap?
body: <p>I know that ES recommends 50% of available memory for the heap, but something about that is confusing me: On a 2GB system, that would give 1GB for ES and 1GB for the OS. </p>
  
  <p>Why on a 8GB system, do we need then to reserve 4GB for the OS rather than 1GB as on the smaller system?</p>
  
  <p>P.S. I was debating whether this question belongs on StackOverflow or ServerFault. If this is the wrong place to post it, just mention it in the comments and I will move it.</p>