I know that Elasticsearch creates a number N of shards per index and that every shard is it's own Lucene index. But how many real instances of Lucene are started and maintained by Elasticsearch?
Is it one Lucene instance per node which would mean that this instance handles N * number_of_indices Lucene indices per node?
Every open shard is an Lucene instance. All primary and replica shards are individual Lucene instances managed by elaticsearch. The number of Lucene instances in the cluster is the total number of primary and replica shards of open indices being held by all member nodes.
Frozen indices are being lazy loaded, so the Lucene instance is only loaded when you query an frozen index and disposed again after the access.
