# Set the number of index segments for indexing
**URL:** https://discuss.elastic.co/t/set-the-number-of-index-segments-for-indexing/18463
**Category:** Elasticsearch
**Created:** [July 3, 2014, 2:04pm UTC](https://discuss.elastic.co/t/set-the-number-of-index-segments-for-indexing/18463 "2014-07-03T14:04:52Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Ophir\_Michaeli](https://discuss.elastic.co/u/Ophir_Michaeli)
#### Post date: [July 3, 2014, 2:04pm UTC](https://discuss.elastic.co/t/set-the-number-of-index-segments-for-indexing/18463/1 "2014-07-03T14:04:52Z")
Hi,
While optimizing it's pretty easy to determine the number of segments by
executing Optimize command with max\_num\_segments parameter.
My question is about indexing prior to optimizing.
I checked the
[http://www.elasticsearch.org/guide/en/elasticsearch/reference/0.90/index-modules-merge.html#tiered](http://www.elasticsearch.org/guide/en/elasticsearch/reference/0.90/index-modules-merge.html#tiered) section
and I still couldn't find - how do I control the number of segments during
indexing? Is there a simple way to tell to ES that I am willing to pay with
indexing time and frequent merges but keep number of segments below 10, for
example?
Thanks,
Ophir
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### Author:  [@jprante](https://discuss.elastic.co/u/jprante)
#### Post date: [July 3, 2014, 4:15pm UTC](https://discuss.elastic.co/t/set-the-number-of-index-segments-for-indexing/18463/2 "2014-07-03T16:15:24Z")
It's a bit more complex. You can use the "segments\_per\_tier" to limit the
number of segments to be created at a tier. Together with
"max\_merge\_at\_once" you can control the amount of running merges.
Mike McCandless is the authority who can explain how the tiered merge
policy works:
> **[Visualizing Lucene's segment merges](https://blog.mikemccandless.com/2011/02/visualizing-lucenes-segment-merges.html)**
>
> If you've ever wondered how Lucene picks segments to merge during indexing, it looks something like this: That video displays segment merges...
Jörg
On Thu, Jul 3, 2014 at 4:04 PM, Ophir Michaeli [ophirmichaeli@gmail.com](mailto:ophirmichaeli@gmail.com)
wrote:
> Hi,
>
> While optimizing it's pretty easy to determine the number of segments by
> executing Optimize command with max\_num\_segments parameter.
> My question is about indexing prior to optimizing.
> I checked the
> [Elasticsearch Platform — Find real-time answers at scale | Elastic](http://www.elasticsearch.org/guide/en/elasticsearch/reference/0.90/index-modules-merge.html#tiered) section
> and I still couldn't find - how do I control the number of segments during
> indexing? Is there a simple way to tell to ES that I am willing to pay with
> indexing time and frequent merges but keep number of segments below 10, for
> example?
>
> Thanks,
> Ophir
>
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> [https://groups.google.com/d/msgid/elasticsearch/3a57e027-1cd3-4578-9421-bf351e833dd4%40googlegroups.com?utm\_medium=email&utm\_source=footer](https://groups.google.com/d/msgid/elasticsearch/3a57e027-1cd3-4578-9421-bf351e833dd4%40googlegroups.com?utm_medium=email&utm_source=footer)
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 6, 2017, 1:18am UTC](https://discuss.elastic.co/t/set-the-number-of-index-segments-for-indexing/18463/3 "2017-07-06T01:18:05Z")