# Index.blocks.read\_only vs Frozen indices

**URL:** <https://discuss.elastic.co/t/index-blocks-read-only-vs-frozen-indices/196994>\
**Category:** Elasticsearch\
**Created:** [August 27, 2019, 7:09pm UTC](https://discuss.elastic.co/t/index-blocks-read-only-vs-frozen-indices/196994 "2019-08-27T19:09:27Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Karthik\_Ramachandran](https://avatars.discourse-cdn.com/v4/letter/k/f19dbf/32.png) [@Karthik\_Ramachandran](https://discuss.elastic.co/u/Karthik_Ramachandran)\
**Post date:** [August 27, 2019, 7:09pm UTC](https://discuss.elastic.co/t/index-blocks-read-only-vs-frozen-indices/196994/1 "2019-08-27T19:09:28Z")

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Trying to clarify between read-only and frozen indices.

We have a indice setting index.blocks.read\_only, and also have Freezing option. Freezing helps with heap, but trying to understand not freezing and setting only the aforementioned setting to true, and performing forcemerge.

Could someone help understand the differences w.r.t impact against cluster performance. What if we set the indice setting to read\_only, force\_merge (NO Freeze) vs force\_merge+Freeze.

References  
[https://www.elastic.co/guide/en/elasticsearch/reference/6.8/indices-forcemerge.html](https://www.elastic.co/guide/en/elasticsearch/reference/6.8/indices-forcemerge.html)  
[https://www.elastic.co/guide/en/elasticsearch/reference/6.8/best\_practices.html](https://www.elastic.co/guide/en/elasticsearch/reference/6.8/best_practices.html)

> **[Creating frozen indices with the Elasticsearch Freeze index API](https://www.elastic.co/blog/creating-frozen-indices-with-the-elasticsearch-freeze-index-api)**
>
> Learn how frozen indices can help release memory on your elasticsearch nodes for data that is rarely queried but still needs to remain searchable. Best practices for freezing elasticsearch indices.

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**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\
**Post date:** [August 30, 2019, 5:14pm UTC](https://discuss.elastic.co/t/index-blocks-read-only-vs-frozen-indices/196994/2 "2019-08-30T17:14:24Z")

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Forcemerging down to a single segment can, as discussed in [this webinar](https://www.elastic.co/webinars/optimizing-storage-efficiency-in-elasticsearch), dramatically reduce the amount of heap used. Freezing the index basically reduces the heap used even further to close to 0. Querying frozen indices require them to be opened, queried and then closed again which is considerably slower. Exactly how much depends a lot on the data and query patterns so I would recommend you test.

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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:** [September 27, 2019, 5:14pm UTC](https://discuss.elastic.co/t/index-blocks-read-only-vs-frozen-indices/196994/3 "2019-09-27T17:14:34Z")

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