# Balancing primary shards

**URL:** <https://discuss.elastic.co/t/balancing-primary-shards/15259>\
**Category:** Elasticsearch\
**Created:** [January 15, 2014, 10:21pm UTC](https://discuss.elastic.co/t/balancing-primary-shards/15259 "2014-01-15T22:21:46Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![iksnalybok](https://avatars.discourse-cdn.com/v4/letter/i/cdc98d/32.png) [@iksnalybok](https://discuss.elastic.co/u/iksnalybok)\
**Post date:** [January 15, 2014, 10:21pm UTC](https://discuss.elastic.co/t/balancing-primary-shards/15259/1 "2014-01-15T22:21:46Z")

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Hi,

this is a very old topic, for which the answer is that balancing primary  
shard is not useful,  
mainly because indexing and replication cost more or less the same.

However, there is a case where it matters: percolation. Our elasticsearch  
infrastructure is  
composed of two nodes. Indexing incomming documents works like a charm, but  
we also  
have around 100 percolators, some of them involving fuzzy matches on  
thousands strings.  
Percolation requires a lot of cpu, a lot more than indexing.  
There are very few search requests, thus their impact on the cpu is  
negligeable.

We observe that, when all primary shards are gathered on one node (e.g.  
badly balanced),  
this node has a very high cpu load, while the other is just quiet. When  
primary shards are  
equally balanced, we observe a similar load on the two nodes.

#3293 has been updated (I cannot reopen it).

Thanks  
ik

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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 6, 2017, 1:56am UTC](https://discuss.elastic.co/t/balancing-primary-shards/15259/2 "2017-07-06T01:56:35Z")

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