Issue
Collections created using the Fusion UI in Managed Fusion environments do not respect the user-defined replication factor. Even when the replication factor is set to 1 during collection creation, the resulting Solr collection may have 2 or more replicas per shard.
Diagnosis
To confirm whether this issue applies:
Create a collection in Fusion UI with replication factor set to 1 and any number of shards.
After creation, inspect the collection status in Solr Admin or via the Fusion Collections API (e.g.,
/api/collections/<collection-name>/status).If you observe 2 or more replicas despite the replication factor being set to 1, the behavior is consistent with Managed Fusion auto-scaling enforcement.
Environment
Fusion 5.9.4+
Lucidworks-hosted Managed Fusion environments only
Cause
This is working as intended. In Managed Fusion deployments, replica count is governed by an autoscaler configuration designed to ensure availability and support autoscaling. This configuration enforces a minimum of two replicas per shard, regardless of user-defined settings in the Fusion UI.
The Fusion UI allows users to specify a replication factor during collection creation. However, in Managed Fusion environments, the backend autoscaler overrides this value to maintain cluster health and redundancy. This behavior is specific to Lucidworks-hosted Fusion and does not occur in self-hosted installations.
Resolution
Understand expected replica behavior
All collections in Lucidworks-hosted environments will be created with at least two replicas per shard regardless of settings in the Fusion UI.
The shard count specified in the Fusion UI is honored and will match the created collection's configuration.
Additional notes
The Fusion UI does not currently provide a warning when replication factor values are overridden in hosted environments.
This behavior does not affect self-hosted Fusion deployments, where the replication factor can be explicitly controlled via Fusion at collection creation time.