Kubelet exposes :

1. kubelet_volume_stats_available_bytes
2. kubelet_volume_stats_inodes
3. kubelet_volume_stats_inodes_used

Those metrics measure information related to a PVC’s filesystem inside a Longhorn block device.

You can set up a monitoring system that scrapes Kubelet metric endpoints to obtains a PVC’s status and set up alerts for abnormal events, such as the PVC being about to run out of storage space.

A popular monitoring setup is prometheus-operator/kube-prometheus-stack, which scrapes metrics and provides a dashboard and alert rules for them.

Longhorn CSI Plugin Support

This allows the kubelet to query the Longhorn CSI plugin for a PVC’s status.

The kubelet then exposes that information in metrics.