Kubernetes Cluster Autoscaler Support (Experimental)
By default, Longhorn blocks Kubernetes Cluster Autoscaler from scaling down nodes because:
For more information, see What types of pods can prevent CA from removing a node?
If you want to unblock the Kubernetes Cluster Autoscaler scaling, you can set the setting Kubernetes Cluster Autoscaler Enabled.
When this setting is enabled, Longhorn will retain the least instance-manager PodDisruptionBudget as possible. Each volume will have at least one replica under the protection of an instance-manager PodDisruptionBudget while no redundant PodDisruptionBudget blocking the Cluster Autoscaler from from scaling down.
When this setting is enabled, Longhorn will also add
cluster-autoscaler.kubernetes.io/safe-to-evict annotation to Longhorn workloads that are not backed by a Kubernetes built-in workload controller or are using local storage mounts.
Warning: Replica rebuilding could be expensive because nodes with reusable replicas could get removed by the Kubernetes Cluster Autoscaler.
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