ES topology

Elastic Stack Elasticsearch
1

Hi,
I have ES 1.7, with two nodes in the cluster:

  1. Master, with this config:
    node.master: true node.data: true
    it sits on a machine with 8 GB RAM and one TB space (I know there's not enough RAM, we're waiting for it to be purchased)
  2. second node, with this config:
    node.master: false node.data: true
    it sits on a machine with 32 GB RAM and one TB space.

I need an advice, should I change the second node to be my master or not?
And if I do make the change, what will happen to the data the current master node?

Thanks for your help!

2

I'd make all 3 master eligible, see https://www.elastic.co/guide/en/elasticsearch/guide/2.x/important-configuration-changes.html#_minimum_master_nodes

3

With only 2 nodes you have 2 scenarios.

  1. Shards that may or may not exist on either node. Here it's probably better to just have a single master.

  2. There's a copy of every shard on both nodes. Here it may make sense to run two masters for HA however you have to be aware of the possibility of a split brain if for some reason the two nodes get partitioned at the network level.

I'd recommend option 3, get a third node so you can set minimum_master_nodes to 2. Failing that if it were me I'd probably stick with a single master as cleaning up a split brain scenario wouldn't be fun.

4

Hi, thanks for the reply.

We will get a third node very soon, and than I think I'll define it as:
node.master: false node.data: false

And then I'll set minimum_master_nodes to 2. What do think?

5

With 3 nodes you should run all of them as masters.

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