Using an Existing SFS File System Through a Static PV

Prerequisites

• You have created a cluster and installed the CCE Container Storage (Everest) add-on in the cluster.
• To create a cluster using commands, ensure kubectl is used. For details, see Connecting to a Cluster Using kubectl.
• You have created an SFS file system that is in the same VPC as the cluster.
• Before using SFS 3.0 for storage, ensure a VPC endpoint has been created in the VPC where the cluster is located for the cluster to access the SFS 3.0 file system. For details, see Configure a VPC Endpoint.

Notes and Constraints

• Multiple PVs can use the same SFS or SFS Turbo file system with the following restrictions:
  • Do not mount the PVCs/PVs that use the same underlying SFS or SFS Turbo volume to one pod. This will lead to a pod startup failure because not all PVCs can be mounted to the pod due to the same volumeHandle value.
  • The persistentVolumeReclaimPolicy parameter in the PVs must be set to Retain. Otherwise, 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.
• If SFS 3.0 is used, the CCE Container Storage (Everest) add-on of v2.0.9 or later must be installed in the cluster.
• If SFS 3.0 is used, the owner group and permission of the mount point cannot be modified. The default owner of the mount point is user root.
• If SFS 3.0 is used, there may be a latency during the creation or deletion of PVCs and PVs. The billing duration is determined by the time when the SFS system is created or deleted on the SFS console.
• If the reclamation policy of SFS 3.0 is set to Delete, PVs and PVCs can be properly deleted only after all files are manually deleted from the mounted SFS system.

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. Choose Storage in the navigation pane. In the right pane, click the PVCs tab. Click Create PVC in the upper right corner. In the dialog box displayed, configure PVC parameters.

      Parameter	Description
      PVC Type	In this example, select SFS.
      PVC Name	Enter the PVC name, which must be unique in a namespace.
      Creation Method	If underlying storage is available, create a PV or use an existing PV to statically create a PVC. 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 both a PV and PVC on the console.
      PVa	Select an existing PV in the cluster. For details about how to create a PV, 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: Only SFS 3.0 is supported.
      Subdirectoryb	Determine whether to use subdirectories to create PVs. Enter the absolute path of a subdirectory, for example, /a/b. Ensure that the subdirectory is available.
      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 prevent the underlying volume from being deleted with a PV.
      Subdirectory Reclaim Policyb	Determine whether to retain subdirectories when a PVC is deleted. This parameter must be used with PV Reclaim Policy and can be configured when PVs are created using subdirectories and PV Reclaim Policy is set to Delete. Retain: If a PVC is deleted, the PV will be deleted, but the subdirectories associated with the PV will be retained. Delete: After a PVC is deleted, the PV and its associated subdirectories will also be deleted.
      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.

      You can choose Storage in the navigation pane and view the created PVC and PV on the PVCs and PVs tab pages, respectively.

3. Create an application.
   1. Choose Workloads in the navigation pane. In the right pane, click the Deployments tab.
   2. Click Create Workload in the upper right corner. 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 specifies a container path to which a data volume will be mounted. Do not mount the volume to a system directory such as / or /var/run. This may lead to 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. Otherwise, the files will be replaced, leading to container startup failures or workload creation failures. NOTICE: If a volume is mounted to a high-risk directory, use an account with minimum permissions to start the container. Otherwise, high-risk files on the host may be damaged.
      Subpath	Enter the subpath of the storage volume and mount a path in the storage volume to the container. In this way, different folders of the same storage volume can be used in a single pod. tmp, for example, indicates that data in the mount path of the container is stored in the tmp folder of the storage volume. If this parameter is left blank, the root path will be used by default.
      Permission	Read-only: You can only read the data in the mounted volumes. Read-write: You can modify the data volumes 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 disk is mounted to the /data path of the container. The container data generated in this path is stored in the SFS file system.

      

   3. After the configuration, 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.

Using an Existing SFS File System Through kubectl

You can select a mode that meets the requirements of your service.

Verifying Data Persistence and Sharing

1. View the deployed application and files.
   1. Run the following command to view the created 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 check the files 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 created 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 files in the /data path of the new pod have 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 created 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