1: primary shard and a replica shard mechanism
(1): index comprising a plurality of shard
(2): Each shard is a minimum unit of work, carrying data portion, ability Lucene example, and the full index resume processing request
(3): increase and decrease node, shard will automatically load balancing nodes in
(4): primary shard and replica shard, there will be only a doc each primary shard and a corresponding replica shard is not possible in the presence of a plurality of primary shard
(5): replica shard is the primary shard copy, responsible for fault tolerance, load and bear a read request
(6): The number of primary shard at the time of creating an index on a fixed number of replica shard can be modified at any time
(7): The default primary shard number is 5, replica shard is 1 by default, default Shard has 10, wherein the primary shard 5 and 5 replica shard
(8): primary shard and a replica shard and its replica shard can not be placed in a node (this provision is to avoid node goes down when, primary shard and a replica shard data are lost, would not achieve the role of fault-tolerant), but other primary shard and a replica shard on the same node
