- With ElasticSearch it is easy to create a lot of indices, nodes, and lots and lots of shards
- Cluster State contains all of the mapping for every index and every field in the cluster
- Loggly.com shared a story where they have a cluster with 900MB of cluster state
- Cluster State is stored and replicated between every node in the cluster
- Since ElasticSearch 2.0, cluster state changes have been sent as differences rather than complete state