# What is a master and data node?

**URL:** <https://discuss.elastic.co/t/what-is-a-master-and-data-node/79703>\
**Category:** Elasticsearch\
**Created:** [March 23, 2017, 8:18am UTC](https://discuss.elastic.co/t/what-is-a-master-and-data-node/79703 "2017-03-23T08:18:00Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![tomer](https://avatars.discourse-cdn.com/v4/letter/t/41988e/32.png) [@tomer](https://discuss.elastic.co/u/tomer)\
**Post date:** [March 23, 2017, 8:18am UTC](https://discuss.elastic.co/t/what-is-a-master-and-data-node/79703/1 "2017-03-23T08:18:00Z")

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I will be happy if some one can explain me what is a master and data node?

P.S.  
I read the [guide](https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-node.html) on nodes but still am confused.

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**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\
**Post date:** [March 23, 2017, 8:22am UTC](https://discuss.elastic.co/t/what-is-a-master-and-data-node/79703/2 "2017-03-23T08:22:56Z")

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A data node holds shards that make up the indices.

A master node makes sure the cluster is stable by taking part in quorum decisions and updating cluster state.

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<div class="post-metadata">

**Author:** ![tomer](https://avatars.discourse-cdn.com/v4/letter/t/41988e/32.png) [@tomer](https://discuss.elastic.co/u/tomer)\
**Post date:** [March 23, 2017, 8:34am UTC](https://discuss.elastic.co/t/what-is-a-master-and-data-node/79703/3 "2017-03-23T08:34:03Z")

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Thanks @warkolm,

Can a master node also be a data node?

Just to be sure:  
From my understanding a data node is basically an object that holds the data (by holding shards that hold data). While the master node is the same type of object that instead of holding data it is in charge of managing the whole cluster. Is this true?

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<div class="post-metadata">

**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\
**Post date:** [March 23, 2017, 8:34am UTC](https://discuss.elastic.co/t/what-is-a-master-and-data-node/79703/4 "2017-03-23T08:34:44Z")

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By default a node is a master (eligible) and a data node.

Your summary is correct.

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [April 20, 2017, 8:34am UTC](https://discuss.elastic.co/t/what-is-a-master-and-data-node/79703/5 "2017-04-20T08:34:48Z")

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