title: How to configure number of shards per cluster in elasticsearch
body: <p>I don't understand the configuration of shards in ES.
  I have few questions about sharding in ES:</p>
  
  <ol>
  <li><p>The number of primary shards is configured through <code>index.number_of_shards</code> parameter, right?</p>
  
  <p>So, it means that the number of shards are configured per index.
  If so, if I have 2 indexes, then I will have 10 shards on the node ?</p></li>
  <li><p>Assuming I have one node (Node 1) that configured with 3 shards and 1 replica.
  Then, I create a new node (Node 2), in the same cluster, with 2 shards.
  So, I assume I will have replica only to two shards, right?</p>
  
  <p>In addition, what happens in case Node 1 is down, how the cluster "knows" that it should have 3 shards instead of 2? Since I have only 2 shards on Node 2, then it means that I lost the data of one of the shards in Node 1 ?</p></li>
  </ol>