# AWS AZ awareness

**URL:** <https://discuss.elastic.co/t/aws-az-awareness/87573>\
**Category:** Elasticsearch\
**Created:** [May 30, 2017, 1:29pm UTC](https://discuss.elastic.co/t/aws-az-awareness/87573 "2017-05-30T13:29:03Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dwjvaughan](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dwjvaughan/32/10648_2.png) [@dwjvaughan](https://discuss.elastic.co/u/dwjvaughan)\
**Post date:** [May 30, 2017, 1:29pm UTC](https://discuss.elastic.co/t/aws-az-awareness/87573/1 "2017-05-30T13:29:03Z")

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Hi,

I have a 5 node, 5.2 cluster currently split over 3 AZs. At the moment, there is no AWS AZ awareness configured. I have two large indices with 5 shards, 1 replica each.

I'm looking to enable awareness, e.g.:

```
node.attr.aws_zone: eu-west-1b
cluster.routing.allocation.awareness.attributes: aws_zone

```

My question is, how will the shards re-distribute? Will the 5th node (in it's own AZ) get some shards from each index? Is it designed to handle a loss of just one AZ? ...and more of an architectural question, would I be better having just two AZs? Or change the number of nodes? I've always been of the mindset that you should have an odd number in a cluster which doesn't works so well in this scenario.

Many thanks,  
Dave

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [June 27, 2017, 1:29pm UTC](https://discuss.elastic.co/t/aws-az-awareness/87573/2 "2017-06-27T13:29:26Z")

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