The repFactor (replication factor) attribute in the indexes.conf file determines whether an index participates in indexer clustering and how many copies of its data are replicated across peer nodes.
When repFactor is set to 0, it explicitly instructs Splunk to exclude that index from participating in the cluster replication and management process. This means:
The index is not replicated across peer nodes.
It will not be managed by the Cluster Manager.
It exists only locally on the indexer where it was created.
Such indexes are typically used for local-only storage, such as _internal, _audit, or other custom indexes that store diagnostic or node-specific data.
By contrast:
repFactor=auto allows the index to inherit the cluster-wide replication policy from the Cluster Manager.
available_sites and site_mappings relate to multisite configurations, controlling where copies of the data are stored, but they do not remove the index from clustering.
Setting repFactor=0 is the only officially supported way to create a non-clustered index within a clustered environment.
References (Splunk Enterprise Documentation):
• indexes.conf Reference – repFactor Attribute Explanation
• Managing Non-Clustered Indexes in Clustered Deployments
• Indexer Clustering: Index Participation and Replication Policies
• Splunk Enterprise Admin Manual – Local-Only and Clustered Index Configurations
