I am trying to understand how many shards I will need for my Elasticsearch cluster. Only recommendation I found is that each shards shouldn't be larger than 30GB, but there is no explanation why. My main concern is search speed right now.
Is a single search for a single Elasticsearch shard uses all CPU cores to rank results or it is a single threaded? I wonder which will be faster to have a single shard with 300GB of data or 10 shards with 30GB each? Lets assume I have 16 cores.
How about sorting and filtering? Are operations on Fielddata performed in parallel?