We have existing Elasticsearch 5.5 cluster and want to migrate to another one Elasticsearch 7+
Mapping is same for both Elasticsearch 5 and Elasticsearch 7 indices
    "mappings": {
        "properties": {
          "_all": {
            "enabled": false
          },
          "keywords_count": {
            "type": "integer"
          },
          "price_sum": {
            "type": "scaled_float",
            "scaling_factor": 100
          },
          "organic": {
            "type": "nested",
            "properties": {
              "position": {
                "type": "short"
              },
              "domain": {
                "type": "keyword"
              },
              "traffic": {
                "type": "integer"
              }
            }
          }
        }
      }
We fill the new index with remote reindex method. Both indices has same number of documents, returned by _cat/count method ( 20 mil ), but additional data from _cat/indices differs a lot
New version has bigger number of docs.count ( 2.6 bil on ES 7 vs 1.1bil on ES 5) and store.size ( 500 gb ES 7 vs 260 gb ES 5)
Cannot understand, what adds so much space requirement? Please help