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Add docs for implementing resize (#5528)

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* Add docs for implementing resize

* Update admission-controllers.md

* Added link to PVC section

* minor typo fixes
This commit is contained in:
Hemant Kumar
2017-09-25 16:14:11 -04:00
committed by Steve Perry
parent f379efa3b4
commit 6ff373e1d9
2 changed files with 64 additions and 1 deletions
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docs/concepts/storage/persistent-volumes.md
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@@ -109,6 +109,39 @@ However, the particular path specified in the custom recycler pod template in th
For volume plugins that support the Delete reclaim policy, deletion removes both the `PersistentVolume` object from Kubernetes, as well as deleting the associated storage asset in the external infrastructure, such as an AWS EBS, GCE PD, Azure Disk, or Cinder volume. Volumes that were dynamically provisioned inherit the [reclaim policy of their `StorageClass`](#reclaim-policy-1), which defaults to Delete. The administrator should configure the `StorageClass` according to users' expectations, otherwise the PV must be edited or patched after it is created. See [Change the Reclaim Policy of a PersistentVolume](https://kubernetes.io/docs/tasks/administer-cluster/change-pv-reclaim-policy/).
### Expanding Persistent Volumes Claims
With Kubernetes 1.8, we have added Alpha support for expanding persistent volumes. The current Alpha support was designed to only support volume types
that don't need file system resizing (Currently only glusterfs).
Administrator can allow expanding persistent volume claims by setting `ExpandPersistentVolumes` feature gate to true. Administrator
should also enable [`PersistentVolumeClaimResize` admission plugin](/docs/admin/admission-controllers/#persistentvolumeclaimresize)
to perform additional validations of volumes that can be resized.
Once `PersistentVolumeClaimResize` admission plug-in has been turned on, resizing will only be allowed for storage classes
whose `allowVolumeExpansion` field is set to true.
``` yaml
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
name: gluster-vol-default
provisioner: kubernetes.io/glusterfs
parameters:
resturl: "http://192.168.10.100:8080"
restuser: ""
secretNamespace: ""
secretName: ""
allowVolumeExpansion: true
```
Once both feature gate and aforementioned admission plug-in are turned on, an user can request larger volume for their `PersistentVolumeClaim`
by simply editing the claim and requesting bigger size. This in turn will trigger expansion of volume that is backing underlying `PersistentVolume`.
Under no circustances a new `PersistentVolume` gets created to satisfy the claim. Kubernetes will attempt to resize existing volume to satisfy the claim.
## Types of Persistent Volumes
`PersistentVolume` types are implemented as plugins. Kubernetes currently supports the following plugins: