# How high availability of elasticsearch cluster?

**URL:** <https://discuss.elastic.co/t/how-high-availability-of-elasticsearch-cluster/161664>\
**Category:** Elasticsearch\
**Created:** [December 20, 2018, 10:49am UTC](https://discuss.elastic.co/t/how-high-availability-of-elasticsearch-cluster/161664 "2018-12-20T10:49:43Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![aymenoss](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/aymenoss/32/38077_2.png) [@aymenoss](https://discuss.elastic.co/u/aymenoss)\
**Post date:** [December 20, 2018, 10:49am UTC](https://discuss.elastic.co/t/how-high-availability-of-elasticsearch-cluster/161664/1 "2018-12-20T10:49:43Z")

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I am going to install elasticsearch 3 node cluster, 2 masters and one node for haut disponibility, my question is I can use the master as data node also or not  
master.node: true  
master.data: true

and what is the problème if I do it ?  
in my case with just one data node, if a problème happen to the data node how can I buckup the data ???????????

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**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\
**Post date:** [December 20, 2018, 10:58am UTC](https://discuss.elastic.co/t/how-high-availability-of-elasticsearch-cluster/161664/2 "2018-12-20T10:58:05Z")

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For high availability you need 3 master-eligible nodes with `discovery.zen.minimum_master_nodes` set to `2`. Having only 2 master-eligible nodes will not give you high availability. You also need at least 2 data nodes and all indices configured to have a replica. The easiest way to do this if all hosts have the same specification is to have all nodes be master-eligible and hold data.

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<div class="post-metadata">

**Author:** ![aymenoss](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/aymenoss/32/38077_2.png) [@aymenoss](https://discuss.elastic.co/u/aymenoss)\
**Post date:** [December 21, 2018, 4:25pm UTC](https://discuss.elastic.co/t/how-high-availability-of-elasticsearch-cluster/161664/3 "2018-12-21T16:25:32Z")

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and for the `discovery.zen.pin.unicast.hosts:["current_host","host2","host3"]`  
if I enter the current host in the list it will not make a problem?????

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [January 18, 2019, 4:36pm UTC](https://discuss.elastic.co/t/how-high-availability-of-elasticsearch-cluster/161664/4 "2019-01-18T16:36:45Z")

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