If you want to query your elasticsearch cluser for disk usage, use this:
curl -XGET "http://localhost:9200/_cat/allocation?v&pretty"
Output:
shards disk.indices disk.used disk.avail disk.total disk.percent host ip node
3213 460.2gb 584.9gb 1.3tb 1.9tb 29 1.1.1.1 1.1.1.1 host1.example.com
3213 479.5gb 599.3gb 1.3tb 1.9tb 29 1.1.1.2 1.1.1.2 host2.example.com
3214 455gb 577.5gb 1.4tb 1.9tb 28 1.1.1.3 1.1.1.3 host3.example.com
3214 465gb 585.6gb 1.3tb 1.9tb 29 1.1.1.4 1.1.1.4 host4.example.com
3213 468.6gb 592.8gb 1.3tb 1.9tb 29 1.1.1.5 1.1.1.5 host5.example.com
3213 461.9gb 582.4gb 1.3tb 1.9tb 28 1.1.1.6 1.1.1.6 host6.example.com
3214 447.9gb 568.9gb 1.4tb 1.9tb 28 1.1.1.7 1.1.1.7 host7.example.com