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add pv protection description (#7620)

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This commit is contained in:
Yuquan Ren
2018-03-05 17:39:51 +08:00
committed by k8s-ci-robot
parent 805f2c7897
commit 90e5519a54
4 changed files with 119 additions and 5 deletions
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docs/concepts/storage/persistent-volumes.md
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@@ -72,14 +72,15 @@ Once a user has a claim and that claim is bound, the bound PV belongs to the use
### Storage Object in Use Protection
{% assign for_k8s_version="v1.10" %}{% include feature-state-beta.md %}
The purpose of the Storage Object in Use Protection feature is to ensure that Persistent Volume Claims (PVCs) in active use by a pod are not removed from the system as this may result in data loss.
The purpose of the Storage Object in Use Protection feature is to ensure that Persistent Volume Claims (PVCs) in active use by a pod and Persistent Volume (PVs) that are bound to PVCs are not removed from the system as this may result in data loss.
**Note:** PVC is in active use by a pod when the pod status is `Pending` and the pod is assigned to a node or the pod status is `Running`.
{: .note}
When the [Storage Object in Use Protection beta feature](/docs/tasks/administer-cluster/pvc-protection/) is enabled, if a user deletes a PVC in active use by a pod, the PVC is not removed immediately. PVC removal is postponed until the PVC is no longer actively used by any pods.
When the [Storage Object in Use Protection beta feature](/docs/tasks/administer-cluster/storage-object-in-use-protection/) is enabled, if a user deletes a PVC in active use by a pod, the PVC is not removed immediately. PVC removal is postponed until the PVC is no longer actively used by any pods, and also if admin deletes a PV that is bound to a PVC, the PV is not removed immediately. PV removal is postponed until the PV is not bound to a PVC any more.
You can see that a PVC is protected when the PVC's status is `Terminating` and the `Finalizers` list includes `kubernetes.io/pvc-protection`:
```shell
kubectl describe pvc hostpath
Name: hostpath
@@ -94,6 +95,28 @@ Finalizers: [kubernetes.io/pvc-protection]
...
```
You can see that a PV is protected when the PV's status is `Terminating` and the `Finalizers` list includes `kubernetes.io/pv-protection` too:
```shell
kubectl describe pv task-pv-volume
Name: task-pv-volume
Labels: type=local
Annotations: <none>
Finalizers: [kubernetes.io/pv-protection]
StorageClass: standard
Status: Available
Claim:
Reclaim Policy: Delete
Access Modes: RWO
Capacity: 1Gi
Message:
Source:
Type: HostPath (bare host directory volume)
Path: /tmp/data
HostPathType:
Events: <none>
```
### Reclaiming
When a user is done with their volume, they can delete the PVC objects from the API which allows reclamation of the resource. The reclaim policy for a `PersistentVolume` tells the cluster what to do with the volume after it has been released of its claim. Currently, volumes can either be Retained, Recycled or Deleted.