Add a note when the node is healthy

Author: xing-yang

keps/sig-storage/2268-non-graceful-shutdown/README.md

@@ -101,6 +101,8 @@ In this section, we are describing the proposed changes to enable workloads to f
 
 Note: The proposal in the current KEP involves user manually add/remove a taint. In the future, we will look into a more automatic approach that does not require these manual steps.
 
+When users verify that a node is already in shutdown or power off state (not in the middle of restarting), either user intentionally shut it down or node is down due to hardware failures, OS issues, they can taint the node with `out-of-service` with `NoExecute` effect.
+
 Existing logic:
 1. When a node is not reachable from the control plane, the health check in Node lifecycle controller, part of kube-controller-manager, sets Node v1.NodeReady Condition to False or Unknown (unreachable) if lease is not renewed for a specific grace period. Node Status becomes NotReady.
 
@@ -119,6 +121,8 @@ Proposed logic change:
 
 1. When the `external-attacher` detects the `volumeAttachment` object is being deleted, it calls CSI driver's `ControllerUnpublishVolume`.
 
+Note: [Existing] If the `out-of-service:NoExecute` taint is applied to a node that is healthy and running, the Taint Manager will try to delete the pods without the matching toleration. Pods will be deleted by Kubelet because the node is healthy and running. New pods will be created on a different running node and application will continue to run.
+
 ### Handle the Return of Shutdown Node
 
 If the nodes that were previously shutdown with pods forcefully deleted come back, we need to make sure they are cleaned up before pods are scheduled on them again.