# Calculating Number of Data nodes

**URL:** <https://discuss.elastic.co/t/calculating-number-of-data-nodes/197545>\
**Category:** Elasticsearch\
**Created:** [August 30, 2019, 3:19pm UTC](https://discuss.elastic.co/t/calculating-number-of-data-nodes/197545 "2019-08-30T15:19:25Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Nikhil04](https://avatars.discourse-cdn.com/v4/letter/n/df705f/32.png) [@Nikhil04](https://discuss.elastic.co/u/Nikhil04)\
**Post date:** [August 30, 2019, 3:19pm UTC](https://discuss.elastic.co/t/calculating-number-of-data-nodes/197545/1 "2019-08-30T15:19:26Z")

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Hi,

I was going through one of the webinars by elastic.In the webinar,I came across a formula to calculate data nodes as below:

Data Nodes: ROUNDUP(Total Storage(GB) / Memory per data node / Memory:data ratio) + 1 Data node for failover capacity

My requirement is as below:

- Total Storage: 10,080 GB
- Memory per node: 64 GB
- Memory:data ratio: 1:30

But when I use above formula(assuming it mentions dividing total storage by memory per data node and then by ratio), my final value for number of data nodes comes out to be 5251 nodes.  
Data Nodes: ROUNDUP(10080/64/(1:30))+ 1

I want to know whether I am calculating this correctly or is there any problem with the formula?

Thanks,  
Nikhil

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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, 4:46pm UTC](https://discuss.elastic.co/t/calculating-number-of-data-nodes/197545/2 "2019-08-30T16:46:56Z")

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> 10,080 / (64 \* 30) = 6 (5.25)

The 1:30 ratio just means that you have 30 times larger storage on the node than you have RAM.

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**Author:** ![Nikhil04](https://avatars.discourse-cdn.com/v4/letter/n/df705f/32.png) [@Nikhil04](https://discuss.elastic.co/u/Nikhil04)\
**Post date:** [August 30, 2019, 7:10pm UTC](https://discuss.elastic.co/t/calculating-number-of-data-nodes/197545/3 "2019-08-30T19:10:51Z")

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Thank you @Christian_Dahlqvist

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**Author:** ![stephenb](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/stephenb/32/40856_2.png) [@stephenb](https://discuss.elastic.co/u/stephenb)\
**Post date:** [August 30, 2019, 9:23pm UTC](https://discuss.elastic.co/t/calculating-number-of-data-nodes/197545/4 "2019-08-30T21:23:56Z")

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@Nikhil04 curious how you came up with the total storage does that include a primary plus one replica of your data or just the primary if so you need to double the total storage so that you can have one primary copy plus one replica copy in order to have HA... l.e. so a loss of a data node does not equal loss of data or make the cluster unusable

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**Author:** ![Nikhil04](https://avatars.discourse-cdn.com/v4/letter/n/df705f/32.png) [@Nikhil04](https://discuss.elastic.co/u/Nikhil04)\
**Post date:** [August 31, 2019, 5:55am UTC](https://discuss.elastic.co/t/calculating-number-of-data-nodes/197545/5 "2019-08-31T05:55:00Z")

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Hi @stephenb,

Yes, Total storage also includes replica.

We have calculated it based on the size of incoming data per day and retention period.

Thanks,  
Nikhil

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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 28, 2019, 5:55am UTC](https://discuss.elastic.co/t/calculating-number-of-data-nodes/197545/6 "2019-09-28T05:55:11Z")

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