# How to measure RAM usage/requirements for ES cluster

**URL:** <https://discuss.elastic.co/t/how-to-measure-ram-usage-requirements-for-es-cluster/39552>\
**Category:** Elasticsearch\
**Created:** [January 19, 2016, 2:48pm UTC](https://discuss.elastic.co/t/how-to-measure-ram-usage-requirements-for-es-cluster/39552 "2016-01-19T14:48:39Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![andreynikk](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/andreynikk/32/6873_2.png) [@andreynikk](https://discuss.elastic.co/u/andreynikk)\
**Post date:** [January 19, 2016, 2:48pm UTC](https://discuss.elastic.co/t/how-to-measure-ram-usage-requirements-for-es-cluster/39552/1 "2016-01-19T14:48:39Z")

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Hi,

currently i'm running ES 1.7.2 on 3 nodes (64 GB RAM, 30GB to ES and rest to cache, 48 cores and 10k rpm HDD disks).  
I know that i currently don't have enough RAM for the use cases of my cluster - ingesting 3 TB of data daily via bulk API. the indexes are created daily and keep 7 days of data. the ES can keep up with the data ingest but the problems start when analysts query the data, and start filling the fielddata. during peek hours i see the JVM Mem usage surpass 85-90%, alot of GC going on, and in HQ i see very high numbers of field evictions and filter evictions and slow refresh and flush on the indexes, up to a point where the ES cluster becomes unresponsive and i need to restart the cluster the clear the cache.

aside from addition of SSD disks, i would like to add more nodes with additional RAM, but i want to have a solid number of the RAM requirements based on my use case. is there a way to calculate how much field data being used? how to calculate ES RAM usage on a period of time (lets say a week?). i know it cant be accurate because of different search requests can have different requirements but I want to have a rough estimate on home much more RAM/nodes should I add.

the only tip i found was here: [3 Performance Tuning Tips For ElasticSearch - EverTrue Engineering](http://evertrue.github.io/blog/2014/11/16/3-performance-tuning-tips-for-elasticsearch/)

> We take the sum of all data node JVM heap sizes  
> We allocate 75% of the heap to indices.fielddata.cache.size  
> As our data set grows, if the utilization starts approaching that 75% barrier, we will add additional data nodes to spread the data and therefore the cache utilization horizontally.

unfortunately i can't add nodes on the fly so i need to know my estimated usage.

any help will be greatly appreciated, thanks!!

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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, 11:23pm UTC](https://discuss.elastic.co/t/how-to-measure-ram-usage-requirements-for-es-cluster/39552/2 "2017-07-05T23:23:26Z")

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