Thanks for pointing us in the right direction. This solves the purpose well.
For getting the total ingested volume, I am using the following query:
GET my_index-2019.01.20/_search
{
"query": {
"match_all": {}
},
"aggs": {
"sizes": {
"sum": {
"field": "_size"
}
}
}
}
The only problem is for large indices (65gb primary volume), the request times out.