MDM does NOT determine shards in each node. The Elastic Search cluster determines that.
Pls check if all 3 nodes are set for node.data=true in elasticsearch.yml file.
Also you can increase the number_of_shards in the index settings of provisioning tool
Thanks for responding Sathiesh,
Our plan is to increase the number_of_shards = 3 in provisioning tool, before that want to understand on what basis ElasticSearch decides these are the 2 nodes which needs to be shared. we see "node.data=true" is set in all 3 nodes.
Please have a look at Yml setting
Pls check how many BEs are enabled for ElasticSearch. If you have only one BE, then only 1 index with 2 shards per your config will be created, so there's no need for 3rd node.
The article shared by Anu explains this behavior well.
If you find this behavior any different than expected you can reach the Elastic forum to get more relevant answers