title: How to speed up refreshes with eager global ordinals
body: <p>I've a 8 nodes cluster (8 r3.xlarge on AWS using the ephemeral 80GB SSD disk coming with the instances). with one main index and two main index types.
  There is a parent/child relationship between them. There are 75M parents and 15M childs. (we cleanup the childs periodically but keep the parents)</p>
  
  <p>In order to speedup the has_child queries, I'm using eager global ordinals on the child's parent field.</p>
  
  <p>Using eager global ordinals seems to significantly slow down the refresh time. A refresh can now take up to 3 seconds.</p>
  
  <p>I believe I can speedup the refreshes by increasing the IO on my machines. But is there any other settings I could play with to fasten the refreshes?</p>
  
  <p>I'm using elasticsearch 1.4.2.</p>
  
  <p>Note that the refreshes were quicker when I was using 8 m3.xlarge with 1 EBS volume. (which doesn't make sense since EBS volumes are supposed to have slower IOs than ephemeral disks...)</p>
  
  <p>Thanks!</p>