Why does a match Persistent Volume not bind to a match Persistent Volume Claim (using k3s)? – Debian

In Kubernetes documentation about Persistent Volumes you can find information that :

A PersistentVolume (PV) is a piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using Storage Classes.

A PersistentVolumeClaim (PVC) is a request for storage by a user. It is similar to a Pod. Pods consume node resources and PVCs consume PV resources.

In Binding section you have information :

Claims will remain unbound indefinitely if a matching volume does not exist. Claims will be bound as matching volumes become available. For example, a cluster provisioned with many 50Gi PVs would not match a PVC requesting 100Gi. The PVC can be bound when a 100Gi PV is added to the cluster.

In Openshift Documentation – Volume and Claim Pre-binding you can find information that when you are using pre-binding you are skipping some matchings.

If you know exactly what PersistentVolume you want your PersistentVolumeClaim to bind to, you can specify the PV in your PVC using the volumeName field. This method skips the normal matching and binding process. The PVC will only be able to bind to a PV that has the same name specified in volumeName. If such a PV with that name exists and is Available, the PV and PVC will be bound regardless of whether the PV satisfies the PVC’s label selector, access modes, and resource requests.

Issue 1

In your PV configuration you set

  capacity:
    storage: 1Mi

which means that you have storage with 1Mi which is ~ 1.04 MB.

Your PVC was configured to request 1Gi which is ~ 1.07GB.

  resources:
    requests:
      storage: 1Gi

Your PV didn’t fulfill your PVC request.

You can have many PV with example 5Gi storage but none of them will be bound if PVC request is higher than 5Gi, like 6Gi. But if PV storage is higher 6Gi and PVC request is lower, like 5Gi it will be bounded, however 1Gi will be wasted.

Issue 2

If you will describe your PVC you will find Warning below:

Events:
  Type     Reason         Age               From                         Message
  ----     ------         ----              ----                         -------
  Warning  FailedBinding  2s (x2 over 17s)  persistentvolume-controller  volume "www-pv" already bound to a different claim.

In your configuration you are using something called Pre-Binding as you have specified volumeName in PVC and claimRef in PV.

This example is well described in OpenShift Documentation – Using Persistent Volumes. In your current setup you’ve used claimRef.name but you didn’t specify claimRef.namespace.

$ kubectl get pv,pvc
NAME                      CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM      STORAGECLASS   REASON   AGE
persistentvolume/www-pv   1Gi        ROX            Retain           Available   /www-pvc                           4m28s

NAME                            STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
persistentvolumeclaim/www-pvc   Pending   www-pv   0                                        4m28s

But when you add claimRef.namespace it will work.

$ kubectl get pv,pvc
NAME                      CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM             STORAGECLASS   REASON   AGE
persistentvolume/www-pv   1Gi        ROX            Retain           Bound    default/www-pvc                           7m3s

NAME                            STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
persistentvolumeclaim/www-pvc   Bound    www-pv   1Gi        ROX                           7m3s

You should specify PVC's namespace in your PV's spec.claimRef.namespace as PVC is namespaced resource.

$ kubectl api-resources | grep pv
persistentvolumeclaims            pvc                                         true         PersistentVolumeClaim
persistentvolumes                 pv                                          false        PersistentVolume

Solution

In your PV change spec.capacity.storage to 1Gi.

In your PV add spec.claimRef.namespace: default like on the example below:

spec:
  storageClassName: ""
  claimRef:
    name: www-pvc
    namespace: default        # adding namespace: defaults
  capacity:
    storage: 1Gi              # changed storage size

Please let me know if you were able to bind PV and PVC.