Can a PVC be bound to a specific PV?

Question

This was discussed by k8s maintainers in https://github.com/kubernetes/kubernetes/issues/7438#issuecomment-97148195:

Allowing users to ask f

Answer 1

Now we can use storageClassName (at least from kubernetes 1.7.x)

See detail https://kubernetes.io/docs/tasks/configure-pod-container/configure-persistent-volume-storage

Copied sample code here as well

kind: PersistentVolume
apiVersion: v1
metadata:
  name: task-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/tmp/data"
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: task-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 3Gi

Answer 2

There is a way to pre-bind PVs to PVCs today, here is an example showing how:

1. Create a PV object with a ClaimRef field referencing a PVC that you will subsequently create:

    $ kubectl create -f pv.yaml
    persistentvolume "pv0003" created
   

   where pv.yaml contains:

    apiVersion: v1
    kind: PersistentVolume
    metadata:
      name: pv0003
    spec:
      storageClassName: ""
      capacity:
        storage: 5Gi
      accessModes:
        - ReadWriteOnce
      persistentVolumeReclaimPolicy: Retain
      claimRef:
        namespace: default
        name: myclaim
      nfs:
        path: /tmp
        server: 172.17.0.2
   

2. Then create the PVC with the same name:

    kind: PersistentVolumeClaim
    apiVersion: v1
    metadata:
      name: myclaim
    spec:
      storageClassName: ""
      accessModes:
        - ReadWriteOnce
      resources:
        requests:
          storage: 5Gi
   

3. The PV and PVC should be bound immediately:

    $ kubectl get pvc
    NAME      STATUS    VOLUME    CAPACITY   ACCESSMODES   AGE
    myclaim   Bound     pv0003    5Gi        RWO           4s
    $ ./cluster/kubectl.sh get pv
    NAME      CAPACITY   ACCESSMODES   STATUS    CLAIM             REASON    AGE
    pv0003    5Gi        RWO           Bound     default/myclaim             57s
   

Answer 3

Yes, you can actually provide the volumeName in the PVC. It will bind exactly to that PV name provided in the volumeName (also spec should be in sync)

Answer 4

storageClassName in PV and PVC should be same. Add the persistent-volume name as volumeName in PVC to bound PVC to a specific PV.

like:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-name
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 40Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/data"
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-name
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  volumeName: pv-name

Answer 5

Better to specify both volumeName in pvc and claimRef in pvc.

By using storageClassName: manual in both pv and pvc we can bind each other, but it does not guarantee if there are many manual pv and pvc's.

Specifying a volumeName in your PVC does not prevent a different PVC from binding to the specified PV before yours does. Your claim will remain Pending until the PV is Available.

Specifying a claimRef in a PV does not prevent the specified PVC from being bound to a different PV. The PVC is free to choose another PV to bind to according to the normal binding process. Therefore, to avoid these scenarios and ensure your claim gets bound to the volume you want, you must ensure that both volumeName and claimRef are specified.

You can tell that your setting of volumeName and/or claimRef influenced the matching and binding process by inspecting a Bound PV and PVC pair for the pv.kubernetes.io/bound-by-controller annotation. The PVs and PVCs where you set the volumeName and/or claimRef yourself will have no such annotation, but ordinary PVs and PVCs will have it set to "yes".

When a PV has its claimRef set to some PVC name and namespace, and is reclaimed according to a Retain reclaim policy, its claimRef will remain set to the same PVC name and namespace even if the PVC or the whole namespace no longer exists.

source: https://docs.openshift.com/container-platform/3.11/dev_guide/persistent_volumes.html

Answer 6

It can be done using the keyword volumeName:

for example

apiVersion: "v1"
kind: "PersistentVolumeClaim"
metadata:
  name: "claimapp80"
spec:
  accessModes:
    - "ReadWriteOnce"
  resources:
    requests:
      storage: "10Gi"
  volumeName: "app080"

will claim specific PV app080