[BUG] Storage Class Configuration Not Applied to PV When Created via Web UI

[roger-ryao]

Describe the bug (🐛 if you encounter this issue)

When I verified issue #6655, I created the storage class longhorn-test using a manifest. Then, I created a volume, PV, and PVC through the Web UI, specifying the Storage Class Name as longhorn-test. However, when I checked the PV YAML output, I couldn't find the longhorn-test configuration applied to the PV.

To Reproduce

1. Created a StorageClass named longhorn-test using a manifest file.

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: longhorn-test
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
parameters:
  numberOfReplicas: "3"
  staleReplicaTimeout: "2880"
  fromBackup: ""
  fsType: "ext4"
  nfsOptions: "hard,timeo=50,retrans=1"

2. Using the Longhorn Web UI, I created a volume and than created volume's PV/PVC, specifying the storageClassName as longhorn-test.
3. However, when I checked the YAML output of the PV, I observed that the configuration related to longhorn-test was not applied to the PV.

apiVersion: v1
kind: PersistentVolume
metadata:
  annotations:
    longhorn.io/volume-scheduling-error: ""
    pv.kubernetes.io/bound-by-controller: "yes"
  creationTimestamp: "2023-09-27T09:31:42Z"
  finalizers:
  - kubernetes.io/pv-protection
  name: vol-6
  resourceVersion: "25956"
  uid: f92c525e-3bce-44e0-a15f-0e33cba90af3
spec:
  accessModes:
  - ReadWriteOnce
  capacity:
    storage: 2Gi
  claimRef:
    apiVersion: v1
    kind: PersistentVolumeClaim
    name: vol-6
    namespace: default
    resourceVersion: "25954"
    uid: 4a8c6d4e-88ac-48a8-80c3-396ac878568a
  csi:
    driver: driver.longhorn.io
    fsType: ext4
    volumeAttributes:
      diskSelector: ""
      nodeSelector: ""
      numberOfReplicas: "3"
      staleReplicaTimeout: "20"
    volumeHandle: vol-6
  persistentVolumeReclaimPolicy: Retain
  storageClassName: longhorn-test
  volumeMode: Filesystem
status:
  phase: Bound

Expected behavior

When user create a volume through the Longhorn WebUI and specify a storageClassName as longhorn-test for the PVC/ PV should also reflect the same storageClassName configuration.

Support bundle for troubleshooting

supportbundle_d76ea023-2256-41d3-98da-c263bd3fad4e_2023-09-27T09-46-58Z.zip

Additional context

#6655
#3506

[m-ildefons]

Hi Roger,
I'm not sure there is a bug here. When you create a volume and then a PV and PVC for that volume, you do static volume provisioning. In that case, the storage class name must match between the PV and PVC, so K8s can bind the two, but otherwise the storage class is ignored, since the volume is already created and the parameters can't necessarily be changed anymore. You could even set the storage class name to "" in this case.
Only if you create the PVC first and let the CSI driver handle the PV and volume, the settings from the storage class will be applied. This is then called dynamic provisioning.

[yangchiu]

With #3506 (comment) and #6802 (comment). Does it mean the Storage Class Name filed on the UI is only applicable when restore a volume from backup? @ChanYiLin