Elasticsearch with two nodes and the default 5 shards?

Question

I have set up a cluster with two nodes but I have some confusions about shard and replica.

What I intend is a setup where there is a master(node A) handling write and a slave(node B) that helps with read and search operation. Ideally if the master is not functional I can recover the data from the slave.

I read that the default is 5 shards and 1 replica. Does it mean that my primary data would then be automatically split between node A and node B. Would that means if one node is down I would lost half the data?

Given the description of my need above, am I doing it right? The only config I have changed at this point is the following

cluster:
  name: maincluster
node:
  name: masternode
  master: true

I am really new to elasticsearch and please kindly point out if I am missing anything.

mconlin mconlin · Accepted Answer · 2014-01-03T12:07:10

5 shards and 1 replica means that your data will be split into 5 shards per index. Each shard will have one replica (5 more backup shards) for a total of 10 shards spread across your set of nodes.

The replica shard will be placed onto a different node than the primary shard (so that if one node fails you have redundancy).

With 2 nodes and replication set to 1 or more, losing a node will still give you access to all of your data, since the primary shard and replication shard will not ever be on same node.

I would install the elasticsearch head plugin it provides a very graphical view of nodes and shards (primary and replica).

Elasticsearch with two nodes and the default 5 shards?

1 Answers