Different size of disk space for cluster nodes

Elastic Stack Elasticsearch
1

If I make cluster with different disk space nodes for example 3 nodes one with 1TB and two with 512GB. and I did shards 3 and replica 1.

How elasticsearch will distribute shards and replica on these different size nodes?
What is 512GB nodes are full. How elasticsearch work in this case?

Regards

2

It'll try to balance everything based on shard count, but if disk space gets too low then the watermarks will likely be hit, see https://www.elastic.co/guide/en/elasticsearch/reference/6.1/disk-allocator.html