Add doc for volume health monitoring

2021-03-15 04:44:44 +00:00
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+---
+reviewers:
+- jsafrane
+- saad-ali
+- msau42
+- xing-yang
+--
+title: Volume Health Monitoring 
+content_type: concept
+---
+
+<!-- overview -->
+
+{{< glossary_tooltip text="CSI" term_id="csi" >}} volume health monitoring allows CSI Drivers to detect abnormal volume conditions from the underlying storage systems and report them as events on {{< glossary_tooltip text="PVCs" term_id="persistent-volume-claim" >}} or {{< glossary_tooltip text="Pods" term_id="pod" >}}.
+
+{{< feature-state for_k8s_version="v1.21" state="alpha" >}}
+
+<!-- body -->
+
+## Volume Health Monitoring
+
+The Volume Health Monitoring feature is part of Kubernetes implementation of Container Storage Interface (CSI). The Volume Health Monitoring feature is implemented in two components: External Health Monitor Controller and Kubelet.
+
+If a CSI Driver supports Volume Health Monitoring feature from the controller side, an event will be reported on the PVC when an abnormal volume condition is detected on a CSI volume.
+
+External Health Monitor Controller will also watch for node failure events. This can be enabled by setting the `enable-node-watcher` flag to true. When a node failure event is detected, an event will be reported on the PVC to indicate that pods using this PVC are on a failed node.
+
+If a CSI Driver supports Volume Health Monitoring feature from the node side, an event will be reported on every Pod using the PVC when an abnormal volume condition is detected on a CSI volume.
+
+Note that you need to enable the `CSIVolumeHealth` feature gate to use this feature from the node side.
+
+See CSI driver [docs](https://kubernetes-csi.github.io/docs/drivers.html) to find out which CSI drivers have implemented this feature.