What is the minimum number of indexers required in a Splunk indexer cluster?

The correct answer is based on the requirements for ensuring fault tolerance and high availability within a Splunk indexer cluster. A minimum of three indexers is necessary to create a reliable environment where data redundancy and availability are maintained.

In an indexer cluster, the primary role of the indexers is to store and process data. With three indexers, you can achieve a quorum for replication and a decision-making process that can endure the loss of one node while still maintaining data integrity and availability. This design allows for both the consistent operation of the cluster and the ability to recover in case of a failure of one indexer.

While having only two indexers might seem sufficient for basic operations, it poses a risk during failures, as there is no mechanism to achieve a quorum. If one node goes down, the cluster could become unavailable or lead to potential data loss. Additionally, configuring an indexer cluster with four indexers may improve performance but is not a requirement for basic functionality or fault tolerance.

Therefore, three indexers strike the right balance between fault tolerance, data availability, and operational reliability, making it the minimum necessary count for a proper indexer cluster setup.