We have ES 2.4 version cluster with 18TB of data (primary + 2 replicas). We have around 12 data nodes with 3TB of disk and 60 GB of RAM ( 30G Heap).
We have around 100 indices of around 30 GB of size.
Our search response time is very high (average 4 sec). Queries are not cached as we don't get very frequent search.
Would increasing File system cache by adding more RAM, say around 150GB would help in search performance?