The maximum number of Elasticsearch master nodes is three. If you specify a
nodeCount greater than
3, OKD creates three Elasticsearch nodes that are Master-eligible nodes, with the master, client, and data roles. The additional Elasticsearch nodes are created as Data-only nodes, using client and data roles. Master nodes perform cluster-wide actions such as creating or deleting an index, shard allocation, and tracking nodes. Data nodes hold the shards and perform data-related operations such as CRUD, search, and aggregations. Data-related operations are I/O-, memory-, and CPU-intensive. It is important to monitor these resources and to add more Data nodes if the current nodes are overloaded.
For example, if
nodeCount=4, the following nodes are created:
$ oc get deployment
cluster-logging-operator 1/1 1 1 18h
elasticsearch-cd-x6kdekli-1 0/1 1 0 6m54s
elasticsearch-cdm-x6kdekli-1 1/1 1 1 18h
elasticsearch-cdm-x6kdekli-2 0/1 1 0 6m49s
elasticsearch-cdm-x6kdekli-3 0/1 1 0 6m44s
The number of primary shards for the index templates is equal to the number of Elasticsearch data nodes.