According to the ElasticSearch glossary, “You cannot change the number of primary shards in an index, once the index is created.” Really? Is that true? (A “primary shard” is what Solr calls a shard, or slice.)
In other words, even though you can easily “add shards” on ES, those are really just replicas of existing primary shards and cannot be new primary shards – if I understand that statement correctly. Besides the simple fact that if a primary shard goes down, a non-primary shard can be promoted to being a primary shard (“a replica shard can be promoted to a primary shard if the primary fails.”) See: http://www.elasticsearch.org/guide/reference/glossary/ My understanding is that with Solr you can do things like split shards and change the number of shards per node. Is this an advantage that ES does not offer? Any ES experts want to comment? -- Jack Krupansky
