# Clarification on shard allocation with 4 nodes across 3 zones using awareness

**URL:** <https://discuss.elastic.co/t/clarification-on-shard-allocation-with-4-nodes-across-3-zones-using-awareness/386077>\
**Category:** Elasticsearch\
**Created:** [April 28, 2026, 3:00pm UTC](https://discuss.elastic.co/t/clarification-on-shard-allocation-with-4-nodes-across-3-zones-using-awareness/386077 "2026-04-28T15:00:09Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![yago82](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/yago82/32/97755_2.png) [@yago82](https://discuss.elastic.co/u/yago82)\
**Post date:** [April 28, 2026, 3:00pm UTC](https://discuss.elastic.co/t/clarification-on-shard-allocation-with-4-nodes-across-3-zones-using-awareness/386077/1 "2026-04-28T15:00:09Z")

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Hi,

I’d like to clarify how shard allocation behaves in a specific setup using shard allocation awareness.

### Cluster setup:

- 4 data nodes

- 3 zones (AZ-A, AZ-B, AZ-C)

- Index: 300 primary shards + 300 replicas (replica count = 1)

- Setting: `cluster.routing.allocation.awareness.attributes: zone`

### Question:

In this configuration, what is the expected shard distribution?

Specifically:

- Does Elasticsearch prioritize even distribution per zone (about 200 shards per zone)?

- Or does it try to balance shards per node (around 150 per node), even if this creates uneven zone distribution?

Thanks in advance for the clarification.

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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:** [April 29, 2026, 6:15am UTC](https://discuss.elastic.co/t/clarification-on-shard-allocation-with-4-nodes-across-3-zones-using-awareness/386077/2 "2026-04-29T06:15:10Z")

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> [@yago82](#):
>
> - Does Elasticsearch prioritize even distribution per zone (about 200 shards per zone)?
> - Or does it try to balance shards per node (around 150 per node), even if this creates uneven zone distribution?

Neither. Each shard only has 2 copies, so with 3 zones allocation awareness ensures that each zone has no more than ⌈2/3⌉ = 1 copy. It does not consider other shards in the same index.