Static Volume Provisioning in Oracle Container Engine for Kubernetes(OKE) with Container Storage Interface(CSI)

Static volume provisioning is useful when you have an existing block volume and you want to make it available in your OKE cluster.

Let’s say the OCID of the block volume which we want to make available to the OKE cluster is `ocid1.volume.oc1.iad.aaaaaaaaaa`, it is of size: 50 Gi and it is in availability domain(AD) US-ASHBURN-AD-1.

Steps for static provisioning:

1. Create a PersistentVolume
2. Create a PersistentVolumeClaim
3. Create a pod to use the PersistentVolumeClaim

1. Create a PersistentVolume

• Use the OCID of the block volume, its size and AD in the following PV manifest: oci_static_pv.yaml

# oci_static_pv.yaml
kind: PersistentVolume
apiVersion: v1
metadata:
  name: static-pv
  annotations:
    pv.kubernetes.io/provisioned-by: blockvolume.csi.oraclecloud.com
spec:
  nodeAffinity:
    required:
      nodeSelectorTerms:
        - matchExpressions:
            - key: failure-domain.beta.kubernetes.io/zone
              operator: In
              values:
                - US-ASHBURN-AD-1
  storageClassName: oci-bv
  persistentVolumeReclaimPolicy: Retain
  capacity:
    storage: 50Gi
  accessModes:
    - ReadWriteOnce
  csi:
    driver: blockvolume.csi.oraclecloud.com
    fsType: ext4
    volumeHandle: ocid1.volume.oc1.iad.aaaaaaaaaa

Run the command:

+ kubectl apply -f oci_static_pv.yaml
persistentvolume/static-pv created
+ kubectl describe pv static-pv
Name:              static-pv
Labels:            <none>
Annotations:       pv.kubernetes.io/provisioned-by: blockvolume.csi.oraclecloud.com
Finalizers:        [kubernetes.io/pv-protection]
StorageClass:      oci-bv
Status:            Available
Claim:
Reclaim Policy:    Retain
Access Modes:      RWO
VolumeMode:        Filesystem
Capacity:          50Gi
Node Affinity:
  Required Terms:
    Term 0:        failure-domain.beta.kubernetes.io/zone in [US-ASHBURN-AD-1]
Message:
Source:
    Type:              CSI (a Container Storage Interface (CSI) volume source)
    Driver:            blockvolume.csi.oraclecloud.com
    FSType:            ext4
    VolumeHandle:      ocid1.volume.oc1.iad.aaaaaaaaaa
    ReadOnly:          false
    VolumeAttributes:  <none>
Events:                <none>

2. Create a PersistentVolumeClaim

• To ensure this PVC gets bind to the PV created in first step, you can choose to set volumeName to <name_of_the_pv> as shown below in oci_static_pvc.yaml.

# oci_static_pvc.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: static-pvc
spec:
  volumeName: static-pv
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 50Gi
  storageClassName: oci-bv

Run the command:

+ kubectl apply -f oci_static_pvc.yaml
persistentvolumeclaim/static-pvc created
 
+ kubectl describe pvc static-pvc
Name:          static-pvc
Namespace:     default
StorageClass:  oci-bv
Status:        Bound
Volume:        static-pv
Labels:        <none>
Annotations:   pv.kubernetes.io/bind-completed: yes
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      50Gi
Access Modes:  RWO
VolumeMode:    Filesystem
Mounted By:    <none>
Events:        <none

3. Create a pod to use the PersistentVolumeClaim

# pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: test-pod
spec:
  containers:
    - name: app
      image: busybox:latest
      command: ["/bin/sh"]
      args: ["-c", "while true; do echo $(date -u) >> /data/out.txt; sleep 5; done"]
      volumeMounts:
        - name: persistent-storage
          mountPath: /data
  volumes:
    - name: persistent-storage
      persistentVolumeClaim:
        claimName: static-pvc

Validate:

+ kubectl apply -f pod.yaml
pod/test-pod created
 
+ kubectl describe pod test-pod
Name:         test-pod
Namespace:    default
Priority:     0
Node:         10.0.10.220/10.0.10.220
Start Time:   Mon, 12 Oct 2020 16:30:52 +0530
Labels:       <none>
Annotations:  Status:  Running
IP:           10.244.0.137
IPs:
  IP:  10.244.0.137
Containers:
  app:
    Container ID:  docker://cf44d8301ed086d63d177a0ba8818f610b858a507c9c61083aba8e1e1ad08f14
    Image:         busybox:latest
    Image ID:      docker-pullable://busybox
    Port:          <none>
    Host Port:     <none>
    Command:
      /bin/sh
    Args:
      -c
      while true; do echo $(date -u) >> /data/out.txt; sleep 5; done
    State:          Running
      Started:      Mon, 12 Oct 2020 16:32:02 +0530
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /data from persistent-storage (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-mgnbz (ro)
Conditions:
  Type              Status
  Initialized       True
  Ready             True
  ContainersReady   True
  PodScheduled      True
Volumes:
  persistent-storage:
    Type:       PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:  static-pvc
    ReadOnly:   false
  default-token-mgnbz:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-mgnbz
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason                  Age        From                     Message
  ----    ------                  ----       ----                     -------
  Normal  Scheduled               <unknown>  default-scheduler        Successfully assigned default/test-pod to 10.0.10.220
  Normal  SuccessfulAttachVolume  49s        attachdetach-controller  AttachVolume.Attach succeeded for volume "static-pv"
  Normal  Pulling                 15s        kubelet, 10.0.10.220     Pulling image "busybox:latest"
  Normal  Pulled                  15s        kubelet, 10.0.10.220     Successfully pulled image "busybox:latest"
  Normal  Created                 15s        kubelet, 10.0.10.220     Created container app
  Normal  Started                 15s        kubelet, 10.0.10.220     Started container app