# Data node JVM Heap not stable

**URL:** <https://discuss.elastic.co/t/data-node-jvm-heap-not-stable/364328>\
**Category:** Elasticsearch\
**Created:** [August 4, 2024, 8:01am UTC](https://discuss.elastic.co/t/data-node-jvm-heap-not-stable/364328 "2024-08-04T08:01:11Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![avnere](https://avatars.discourse-cdn.com/v4/letter/a/ba8739/32.png) [@avnere](https://discuss.elastic.co/u/avnere)\
**Post date:** [August 4, 2024, 8:01am UTC](https://discuss.elastic.co/t/data-node-jvm-heap-not-stable/364328/1 "2024-08-04T08:01:11Z")

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Hi

I Have cluster with 3 data nodes + 1 master node.  
I noticed that in Idle the JVM heap of data node is not stable and jumping between 16GB to 25GB. Please see below.

Why it is happening?  
Is it normal behavior?

![jvmHeap](https://us1.discourse-cdn.com/elastic/original/3X/0/3/0390280abafa4e170cbd6d8735d09eefbbd627d6.png)

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<div class="post-metadata">

**Author:** ![DavidTurner](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/davidturner/32/22453_2.png) [@DavidTurner](https://discuss.elastic.co/u/DavidTurner)\
**Post date:** [August 4, 2024, 9:10am UTC](https://discuss.elastic.co/t/data-node-jvm-heap-not-stable/364328/2 "2024-08-04T09:10:36Z")

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> [@avnere](#):
>
> I Have cluster with 3 data nodes + 1 master node.

Don't do that. If you only have 3-4 nodes just make them all do everything. Dedicated master nodes are unnecessary for such a small cluster. If you only have one master node then it will eventually fail, destroying your cluster in the process. See [these docs](https://www.elastic.co/guide/en/elasticsearch/reference/current/high-availability-cluster-design.html) for more info.

> [@avnere](#):
>
> Is it normal behavior?

Not unexpected for sure, see e.g. [this blog post](https://www.elastic.co/blog/found-understanding-memory-pressure-indicator).