Graylog Indexs disk limit

grayog web interface was receiving 502 bad gateway issues. When I checked I found My ELasticache in red state.

{"cluster_name":"graylog","status":"red","timed_out":false,"number_of_nodes":1,"number_of_data_nodes":1,"active_primary_shards":0,"active_shards":0,"relocating_shards":0,"initializing_shards":4,"unassigned_shards":24,"delayed_unassigned_shards":0,"number_of_pending_tasks":7,"number_of_in_flight_fetch":1,"task_max_waiting_in_queue_millis":11,"active_shards_percent_as_number":0.0|

Output of sudo curl -XGET localhost:9200/_cat/shards:

graylog_6 3 p UNASSIGNED
graylog_6 2 p UNASSIGNED
graylog_6 1 p INITIALIZING   127.0.0.1 Chronos
graylog_6 0 p INITIALIZING   127.0.0.1 Chronos
graylog_1 1 p UNASSIGNED
graylog_1 2 p UNASSIGNED
graylog_1 3 p UNASSIGNED
graylog_1 0 p UNASSIGNED
graylog_0 3 p UNASSIGNED
graylog_0 2 p UNASSIGNED
graylog_0 1 p UNASSIGNED
graylog_0 0 p UNASSIGNED
graylog_5 3 p UNASSIGNED
graylog_5 2 p INITIALIZING   127.0.0.1 Chronos
graylog_5 1 p INITIALIZING   127.0.0.1 Chronos
graylog_5 0 p UNASSIGNED
graylog_4 1 p UNASSIGNED
graylog_4 2 p UNASSIGNED
graylog_4 3 p UNASSIGNED
graylog_4 0 p UNASSIGNED
graylog_3 3 p UNASSIGNED
graylog_3 2 p UNASSIGNED
graylog_3 1 p UNASSIGNED
graylog_3 0 p UNASSIGNED
graylog_2 3 p UNASSIGNED
graylog_2 2 p UNASSIGNED
graylog_2 1 p UNASSIGNED
graylog_2 0 p UNASSIGNED
curl  http://localhost:9200/_stats/index,store?pretty
{
  "_shards" : {
    "total" : 28,
    "successful" : 1,
    "failed" : 0
  },
  "_all" : {
    "primaries" : {
      "store" : {
        "size_in_bytes" : 354842957,
        "throttle_time_in_millis" : 0
      }
    },
    "total" : {
      "store" : {
        "size_in_bytes" : 354842957,
        "throttle_time_in_millis" : 0
      }
    }
  },
  "indices" : {
    "graylog_6" : {
      "primaries" : {
        "store" : {
          "size_in_bytes" : 354842957,
          "throttle_time_in_millis" : 0
        }
      },
      "total" : {
        "store" : {
          "size_in_bytes" : 354842957,
          "throttle_time_in_millis" : 0
        }
      }
    }
  }
}
curl 'localhost:9200/_cat/indices?v'
health status index     pri rep docs.count docs.deleted store.size pri.store.size
red    open   graylog_6   4   0
red    open   graylog_1   4   0
red    open   graylog_0   4   0
red    open   graylog_5   4   0
red    open   graylog_4   4   0
red    open   graylog_3   4   0
red    open   graylog_2   4   0
40M	./graylog_0
6.1G	./graylog_1
40G	./graylog_2
21G	./graylog_3
220K	./graylog_4
2.3M	./graylog_5
3.3G	./graylog_6
70G	total

What should I do.How to fix disk out of space.The I have only 75GB in total.How can I make server up.Do i need to delete all the indexes.What would happen if the indexes are deleted. Should I add more diskspace.I am very beginner with graylog, Is it safe to delete some indexes

This depends on whether you want to keep all the log messages you’ve indexed so far.

As long as you’ll use the official Elasticsearch Delete Index API, it should be safe: https://www.elastic.co/guide/en/elasticsearch/reference/2.4/indices-delete-index.html

After deleting the indexes cluster status become green.Thank you