In an 14 node, RAID 5 based Elasticsearch cluster, the search performance does not improve no matter how simple the full-text query is.
There are two indices: one is 30 shard, 1 replica, 1.1tb and 110M document size. The other is 200 shard, 1 replica, 8.4tb and 663M document size. In both of them, the average query time does not seem to be lower than 700 ms.
The query is basically a multi_match query in few different fields.
What could be the reason?