CODEWITHSUNDEEP
elasticsearch
MaatDeamon
MaatDeamon

Reputation: 9761

How to avoid or minimize a split brain with 3 nodes in Elasticsearch

I try to read the different recommendations here and there, but I still don't see how with 3 nodes we solve the problem over two nodes.

If I have A<->B<->C<->A node and A <-> B network connection is down, how to avoid the possibility to form 2 clusters A <-> C and B <-> C running in parallel?

Upvotes: 3

Views: 1979

Answers (1)

Sobrique
Sobrique

Reputation: 53478

A split brain scenario occurs when some of your cluster nodes can't connect to other cluster nodes.

With a large estate - especially geographically distributed - the intermediate link might be lost. If both parts of the cluster are quorate (have enough nodes available as defined in the config) they carry on 'working' and you end up with data going out of sync between the two.

This cannot happen in your scenario, because node C knows that both A and B are online - thus you don't get two separate clusters forming, even if the comms between A and B are offline.

If A was lost entirely, B+C are more than 50% of the nodes - therefore your cluster knows it's 'quorate' and can continue operating normally.

Enhancements to Zen discovery fixing partial isolation

Upvotes: 4

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