kubernetes - 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 for a specific PV breaks the separation between them

I don't buy that. We allow users to choose a node. It's not the common case, but it exists for a reason.

How did it end? What's the intended way to have >1 PV's and PVC's like the one in https://github.com/kubernetes/kubernetes/tree/master/examples/nfs?

We use NFS, and PersistentVolume is a handy abstraction because we can keep the server IP and the path there. But a PersistentVolumeClaim gets any PV with sufficient size, preventing path reuse.

Can set volumeName in a PVC spec block (see https://github.com/kubernetes/kubernetes/pull/7529) but it makes no difference.

Answer 1

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