Using an Existing File System Through a Static PV

Prerequisites

• If you want to create a cluster using commands, use kubectl to connect to the cluster. For details, see Connecting to a Cluster Using kubectl.
• You have created a file system that is in the same VPC as the cluster.

Constraints

• Multiple PVs can use the same SFS or SFS Turbo file system, but there are some constraints.
  • Do not mount all PVCs/PVs that use the same SFS or SFS Turbo file system to a pod. This will result in a pod startup failure because not all PVCs can be mounted to the pod due to the same volumeHandle values of these PVs.
  • The persistentVolumeReclaimPolicy parameter in the PVs should be set to Retain. If any other value is used, when a PV is deleted, the associated underlying volume may be deleted. In this case, other PVs associated with the underlying volume malfunction.
  • When the underlying volume is repeatedly used, enable isolation and protection for ReadWriteMany at the application layer to prevent data overwriting and loss.

Using an Existing SFS File System on the Console

1. Log in to the CCE console and click the cluster name to access the cluster console.
2. Statically create a PVC and PV.
   1. In the navigation pane on the left, choose Storage. Then click the PVCs tab. In the upper right corner, click Create PVC. In the displayed dialog box, configure the parameters.

      Parameter	Description
      PVC Type	In this example, select SFS.
      PVC Name	Enter the PVC name, which must be unique in the same namespace.
      Creation Method	If underlying storage is available, create a storage volume or use an existing storage volume to statically create a PVC based on whether a PV is available. If no underlying storage is available, select Dynamically provision. For details, see Using an SFS File System Through a Dynamic PV. In this example, select Create new to create a PV and PVC at the same time on the console.
      PVa	Select an existing PV in the cluster. Create a PV in advance. For details, see "Creating a storage volume" in Related Operations. You do not need to specify this parameter in this example.
      SFSb	Click Select SFS. On the displayed page, select the SFS file system that meets your requirements and click OK. NOTE: Currently, only SFS 3.0 is supported.
      PV Nameb	Enter the PV name, which must be unique in the same cluster.
      Access Modeb	SFS volumes support only ReadWriteMany, indicating that a storage volume can be mounted to multiple nodes in read/write mode. For details, see Volume Access Modes.
      Reclaim Policyb	You can select Delete or Retain to specify the reclaim policy of the underlying storage when the PVC is deleted. For details, see PV Reclaim Policy. NOTE: If multiple PVs use the same underlying storage volume, use Retain to avoid cascading deletion of underlying volumes.
      Mount Optionsb	Enter the mounting parameter key-value pairs. For details, see Configuring SFS Volume Mount Options.

      

      a: The parameter is available when Creation Method is set to Use existing.

      b: The parameter is available when Creation Method is set to Create new.

   2. Click Create to create a PVC and a PV.

      In the navigation pane on the left, choose Storage. View the created PVC and PV on the PVCs and PVs tabs, respectively.

3. Create a workload.
   1. In the navigation pane on the left, choose Workloads. Then click the Deployments tab.
   2. In the upper right corner, click Create Workload. On the displayed page, click Data Storage in the Container Settings area and click Add Volume to select PVC.
      Mount and use storage volumes, as shown in Table 1. For details about other parameters, see Workloads.

      Table 1 Mounting a storage volume

      Parameter	Description
      PVC	Select an existing SFS volume.
      Mount Path	Enter a mount path, for example, /tmp. This parameter indicates the container path that the volume will be mounted to. Do not mount the volume to a system directory such as / or /var/run. This may cause container errors. Mount the volume to an empty directory. If the directory is not empty, ensure that there are no files that affect container startup. If there are such files, they will be replaced, which will lead to a container startup or workload creation failure. NOTICE: If a volume is mounted to a high-risk directory, use an account with minimum permissions to start the container, or high-risk files on the host may be damaged.
      Subpath	Enter a subpath, for example, tmp, indicating that data in the mount path of the container is stored in the tmp directory of the storage volume. A subpath is used to mount a local volume so that the same data volume is used in a single pod. If this parameter is left blank, the root path is used by default.
      Permission	Read-only: You can only read the data in the mounted volume. Read-write: You can modify the volume mounted to the path. Newly written data will not be migrated if the container is migrated, which may cause data loss.

      In this example, the volume is mounted to the /data path of the container. The container data generated in this path is stored in the SFS file system.

      

   3. Configure other parameters and click Create Workload.

      After the workload is created, the data in the container mount directory will be persistently stored. Verify the storage by referring to Verifying Data Persistence and Sharing.

(kubectl) Using an Existing SFS File System

1. Use kubectl to connect to the cluster.
2. Create a PV.
   1. Create the pv-sfs.yaml file.

      apiVersion: v1
      kind: PersistentVolume
      metadata:
        annotations:
          pv.kubernetes.io/provisioned-by: everest-csi-provisioner
          everest.io/reclaim-policy: retain-volume-only      # (Optional) The PV is deleted while the underlying volume is retained.
        name: pv-sfs    # PV name.
      spec:
        accessModes:
        - ReadWriteMany      # Access mode. The value must be ReadWriteMany for SFS.
        capacity:
          storage: 1Gi     # SFS volume capacity.
        csi:
          driver: nas.csi.everest.io    # Dependent storage driver for the mounting
          fsType: nfs
      volumeHandle: <your_volume_id> # Enter the SFS volume name if SFS 3.0 is used.
          volumeAttributes:
            everest.io/share-export-location: <your_location>  # Shared path of the SFS volume.
            storage.kubernetes.io/csiProvisionerIdentity: everest-csi-provisioner
            everest.io/sfs-version: sfs3.0       # SFS 3.0 is used.
        persistentVolumeReclaimPolicy: Retain    # Reclaim policy.
        storageClassName: csi-sfs               # Storage class name. csi-sfs indicates that SFS 3.0 is used.
        mountOptions: []                         # Mount options.

      Table 2 Key parameters

      Parameter	Mandatory	Description
      everest.io/reclaim-policy: retain-volume-only	No	Optional. Currently, only retain-volume-only is supported. This parameter is valid only when the reclaim policy is set to Delete. If the reclaim policy is Delete and the value is retain-volume-only, the associated PV is deleted while the underlying storage volume is retained, when a PVC is deleted.
      volumeHandle	Yes	If an SFS 3.0 file system is used, enter the file system name.
      everest.io/share-export-location	Yes	Shared path of the file system. A shared path is in the following format: {your_sfs30_name}.sfs3.{region}.myhuaweicloud.com:/{your_sfs30_name}
      mountOptions	Yes	Mount options. If this parameter is not specified, the following configurations are used by default. For details, see Configuring SFS Volume Mount Options. mountOptions: - vers=3 - timeo=600 - nolock - hard
      persistentVolumeReclaimPolicy	Yes	The Delete and Retain reclaim policies are supported. For details, see PV Reclaim Policy. If multiple PVs use the same SFS volume, use Retain to prevent the underlying volume from being deleted with a PV. Delete: If everest.io/reclaim-policy is not specified, both the PV and SFS file sytem will be deleted when a PVC is deleted. If everest.io/reclaim-policy is set to retain-volume-only, when a PVC is deleted, the PV will be deleted but the SFS file system will be retained. Retain: When a PVC is deleted, the PV and underlying storage resources are not deleted. Instead, you must manually delete these resources. After that, the PV is in the Released state and cannot be bound to a PVC again.
      storage	Yes	Requested capacity in the PVC, in Gi. For SFS, this field is used only for verification (cannot be empty or 0). Its value is fixed at 1, and any value you set does not take effect for SFS file systems.

   2. Run the following command to create a PV:

      kubectl apply -f pv-sfs.yaml

3. Create a PVC.
   1. Create the pvc-sfs.yaml file.

      apiVersion: v1
      kind: PersistentVolumeClaim
      metadata:
        name: pvc-sfs
        namespace: default
        annotations:
          volume.beta.kubernetes.io/storage-provisioner: everest-csi-provisioner
      spec:
        accessModes:
        - ReadWriteMany               # The value must be ReadWriteMany for SFS.
        resources:
          requests:
            storage: 1Gi               # SFS volume capacity.
        storageClassName: csi-sfs       # Storage class name, which must be the same as that of the PV.
        volumeName: pv-sfs    # PV name.

      Table 3 Key parameters

      Parameter	Mandatory	Description
      storage	Yes	Requested capacity in the PVC, in Gi. The value must be the same as the storage size of the existing PV.
      volumeName	Yes	PV name, which must be the same as the PV name in 2.a.

   2. Run the following command to create a PVC:

      kubectl apply -f pvc-sfs.yaml

4. Create a workload.
   1. Create a file named web-demo.yaml. In this example, the SFS volume is mounted to the /data path.

      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: web-demo
        namespace: default
      spec:
        replicas: 2
        selector:
          matchLabels:
            app: web-demo
        template:
          metadata:
            labels:
              app: web-demo
          spec:
            containers:
            - name: container-1
              image: nginx:latest
              volumeMounts:
              - name: pvc-sfs-volume    # Volume name, which must be the same as the volume name in the volumes field.
                mountPath: /data  # Location where the storage volume is mounted.
            imagePullSecrets:
              - name: default-secret
            volumes:
              - name: pvc-sfs-volume    # Custom volume name
                persistentVolumeClaim:
                  claimName: pvc-sfs    # Name of the created PVC.

   2. Run the following command to create a workload the SFS volume is mounted to:

      kubectl apply -f web-demo.yaml

      After the workload is created, the data in the container mount directory will be persistently stored. Verify the storage by referring to Verifying Data Persistence and Sharing.

Verifying Data Persistence and Sharing

1. View the deployed application and files.
   1. Run the following command to view the pod:

      kubectl get pod | grep web-demo

      Expected output:

      web-demo-846b489584-mjhm9   1/1     Running   0             46s
      web-demo-846b489584-wvv5s   1/1     Running   0             46s

   2. Run the following commands in sequence to view the files in the /data path of the pods:

      kubectl exec web-demo-846b489584-mjhm9 -- ls /data
      kubectl exec web-demo-846b489584-wvv5s -- ls /data

      If no result is returned for both pods, no file exists in the /data path.

2. Run the following command to create a file named static in the /data path:

   kubectl exec web-demo-846b489584-mjhm9 --  touch /data/static

3. Run the following command to view the created file in the /data path:

   kubectl exec web-demo-846b489584-mjhm9 -- ls /data

   Expected output:

   static

4. Verify data persistence.
   1. Run the following command to delete the pod named web-demo-846b489584-mjhm9:

      kubectl delete pod web-demo-846b489584-mjhm9

      Expected output:

      pod "web-demo-846b489584-mjhm9" deleted

      After the deletion, the Deployment controller automatically creates a replica.

   2. Run the following command to view the pod:

      kubectl get pod | grep web-demo

      The expected output is as follows, in which web-demo-846b489584-d4d4j is the newly created pod:

      web-demo-846b489584-d4d4j   1/1     Running   0             110s
      web-demo-846b489584-wvv5s    1/1     Running   0             7m50s

   3. Run the following command to check whether the file in the /data path of the new pod has been modified:

      kubectl exec web-demo-846b489584-d4d4j -- ls /data

      Expected output:

      static

      The static file is retained, indicating that the data in the file system can be stored persistently.

5. Verify data sharing.
   1. Run the following command to view the pod:

      kubectl get pod | grep web-demo

      Expected output:

      web-demo-846b489584-d4d4j   1/1     Running   0             7m
      web-demo-846b489584-wvv5s   1/1     Running   0             13m

   2. Run the following command to create a file named share in the /data path of either pod: In this example, select the pod named web-demo-846b489584-d4d4j.

      kubectl exec web-demo-846b489584-d4d4j --  touch /data/share

      Check the files in the /data path of the pod.

      kubectl exec web-demo-846b489584-d4d4j -- ls /data

      Expected output:

      share
      static

   3. Check whether the share file exists in the /data path of another pod (web-demo-846b489584-wvv5s) as well to verify data sharing.

      kubectl exec web-demo-846b489584-wvv5s -- ls /data

      Expected output:

      share
      static

      After you create a file in the /data path of a pod, if the file is also created in the /data path of the other pod, the two pods share the same volume.

Related Operations