How to choose shards, replicas and cluster size: Rules of Thumb.
sh = shards rf = replication factor. replicas = 0 implies rf = 1, or 1 replica of each shard.
pm = running data_esnode processes per machine N = number of machines
n_cores = number of cpu cores per machine n_disks = number of disks per machine
You must have at least as many data_esnodes as Mandatory: (sh * rf) < (pm * N)
Shards: shard size < 10GB
More shards = more parallel writes