Kubernetes NFS Persistent Volumes - multiple claims on same volume? Claim stuck in pending?

Question

Use case:

I have a NFS directory available and I want to use it to persist data for multiple deployments & pods.

I have created a PersistentVolume:

apiVersion: v1 kind: PersistentVolume metadata:   name: nfs-pv spec:   capacity:     storage: 10Gi   accessModes:     - ReadWriteMany   nfs:     server: http://mynfs.com     path: /server/mount/point 

I want multiple deployments to be able to use this PersistentVolume, so my understanding of what is needed is that I need to create multiple PersistentVolumeClaims which will all point at this PersistentVolume.

kind: PersistentVolumeClaim apiVersion: v1 metaData:   name: nfs-pvc-1   namespace: default spec:   accessModes:     - ReadWriteMany   resources:     requests:       storage: 50Mi 

I believe this to create a 50MB claim on the PersistentVolume. When I run kubectl get pvc, I see:

NAME        STATUS     VOLUME    CAPACITY    ACCESSMODES   AGE nfs-pvc-1   Bound      nfs-pv    10Gi        RWX           35s 

I don't understand why I see 10Gi capacity, not 50Mi.

When I then change the PersistentVolumeClaim deployment yaml to create a PVC named nfs-pvc-2 I get this:

NAME        STATUS     VOLUME    CAPACITY    ACCESSMODES   AGE nfs-pvc-1   Bound      nfs-pv    10Gi        RWX           35s nfs-pvc-2   Pending                                        10s 

PVC2 never binds to the PV. Is this expected behaviour? Can I have multiple PVCs pointing at the same PV?

When I delete nfs-pvc-1, I see the same thing:

NAME        STATUS     VOLUME    CAPACITY    ACCESSMODES   AGE nfs-pvc-2   Pending                                        10s 

Again, is this normal?

What is the appropriate way to use/re-use a shared NFS resource between multiple deployments / pods?

Answer 1

Basically you can't do what you want, as the relationship PVC <--> PV is one-on-one.

If NFS is the only storage you have available and would like multiple PV/PVC on one nfs export, use Dynamic Provisioning and a default storage class.

It's not in official K8s yet, but this one is in the incubator and I've tried it and it works well: https://github.com/kubernetes-incubator/external-storage/tree/master/nfs-client

This will enormously simplify your volume provisioning as you only need to take care of the PVC, and the PV will be created as a directory on the nfs export / server that you have defined.

Answer 2

From: https://docs.openshift.org/latest/install_config/storage_examples/shared_storage.html

As Baroudi Safwen mentioned, you cannot bind two pvc to the same pv, but you can use the same pvc in two different pods.

volumes: - name: nfsvol-2   persistentVolumeClaim:     claimName: nfs-pvc-1 <-- USE THIS ONE IN BOTH PODS