Do all the hosts have the same hardware specification and amount of storage available? Are you using node attributes to control sharing through shard allocation filtering and/or awareness (see the [cat nodeattrs API](https://www.elastic.co/guide/en/elasticsearch/reference/6.4/cat-nodeattrs.html))? What does the [cat nodes API](https://www.elastic.co/guide/en/elasticsearch/reference/6.4/cat-nodes.html) show?

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