# Index\_buffer\_size vs max\_index\_buffer\_size

**URL:** <https://discuss.elastic.co/t/index-buffer-size-vs-max-index-buffer-size/39586>\
**Category:** Elasticsearch\
**Created:** [January 19, 2016, 6:58pm UTC](https://discuss.elastic.co/t/index-buffer-size-vs-max-index-buffer-size/39586 "2016-01-19T18:58:15Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Chris\_Fraschetti](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@Chris\_Fraschetti](https://discuss.elastic.co/u/Chris_Fraschetti)\
**Post date:** [January 19, 2016, 6:58pm UTC](https://discuss.elastic.co/t/index-buffer-size-vs-max-index-buffer-size/39586/1 "2016-01-19T18:58:15Z")

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I'm currently running ES 1.7.1 although the docs for this haven't changed so I'm not sure that's relevant.

The docs for these settings give a fairly decent explanation of these settings but it's a bit unclear why max\_index\_buffer\_size would be required if index\_buffer\_size has been set.

> **indices.memory.index\_buffer\_size**  
> Accepts either a percentage or a byte size value. It defaults to 10%, meaning that 10% of the total heap allocated to a node will be used as the indexing buffer size shared across all shards.

> **indices.memory.min\_index\_buffer\_size**  
> If the index\_buffer\_size is specified as a percentage, then this setting can be used to specify an absolute minimum. Defaults to 48mb.

> **indices.memory.max\_index\_buffer\_size**  
> If the index\_buffer\_size is specified as a percentage, then this setting can be used to specify an absolute maximum. Defaults to unbounded.

Example:  
ES heap size is 10g  
index\_buffer\_size is set to 10%

I'd assume that implies ES will share 1g of heap among the shards currently indexing.  
I'd also assume that implies a max of 10% (1g) but then why would max\_index\_buffer\_size exist.

Questions:

1. Does "shared across all shards" imply just shards from indices currently doing indexing or does this imply all shards from all open indices share this memory?

2. How does index\_buffer\_size truly differ from max\_index\_buffer\_size?

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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:** [January 20, 2016, 8:56am UTC](https://discuss.elastic.co/t/index-buffer-size-vs-max-index-buffer-size/39586/2 "2016-01-20T08:56:30Z")

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The min and max are taken into account only when index\_buffer\_size is a percentage. In that case the min and max may override index\_buffer\_size depending on how much memory is available.

I'll see if we can get the docs updated to reflect this.

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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:** [July 5, 2017, 11:23pm UTC](https://discuss.elastic.co/t/index-buffer-size-vs-max-index-buffer-size/39586/3 "2017-07-05T23:23:06Z")

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