# Why use shards and not replica shards?

**URL:** <https://discuss.elastic.co/t/why-use-shards-and-not-replica-shards/44413>\
**Category:** Elasticsearch\
**Created:** [March 15, 2016, 9:49am UTC](https://discuss.elastic.co/t/why-use-shards-and-not-replica-shards/44413 "2016-03-15T09:49:02Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dorr](https://avatars.discourse-cdn.com/v4/letter/d/d2c977/32.png) [@dorr](https://discuss.elastic.co/u/dorr)\
**Post date:** [March 15, 2016, 9:49am UTC](https://discuss.elastic.co/t/why-use-shards-and-not-replica-shards/44413/1 "2016-03-15T09:49:02Z")

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Hello,

Let's assume I have _k_ indices, each with one shard, running on a single node. The performance is good.  
I want to add more nodes, and for that - I'll need replicas.

What is the benefit of using shards and not replica shards, assuming index size fits well in a shard?  
The ability to change the amount of replicas after index creation is great and I'm wondering why not use it.  
I am assuming that replica shards can answer search queries as the documentation states.

When would I regret defining only a single shard per index, other than in case of data growth inside an index?

Thanks,  
Dor.

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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:** [July 5, 2017, 11:08pm UTC](https://discuss.elastic.co/t/why-use-shards-and-not-replica-shards/44413/2 "2017-07-05T23:08:24Z")

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