Creating an Elasticsearch Cluster with Dedicated Master
When creating a cluster, you can choose to provision three dedicated master nodes with the cluster.
When should I use dedicated master nodes?
We strongly recommend using dedicated master nodes for production clusters with more than 3 nodes.
How do dedicated master nodes work?
Normally, all nodes are master-eligible; any node can be involved in handling queries and managing cluster state. If nodes are under heavy load, the master node may be overwhelmed, causing severe problems for the whole cluster. When dedicated master nodes are enabled, we provision three nodes that are master-eligible, but do not participate in searching and indexing. This ensures that the master node remains responsive even when the cluster is under heavy load. If the master node fails, another of the three will automatically be chosen.
What size should the dedicated masters be?
Unless you have specific requirements (eg, you know from previous experience that your workload is particularly intensive on master nodes), you should choose the smallest dedicated master node type available. We can adjust the node size later based on your requirements.
Since larger data nodes will be handling more difficult traffic, there is a constraint: dedicated master nodes must have at least 25% as much RAM as data nodes. Node choices that do not meet this constraint will be greyed out.