This section describes how to use storage classes to dynamically create PVs and PVCs and implement data persistence and sharing in workloads.

Prerequisites

You have created a cluster and installed the CCE Container Storage (Everest) add-on in the cluster.
Before creating a cluster using commands, ensure kubectl is used to access the cluster. 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.

Automatically Creating an SFS File System on the Console

Dynamically create a PVC and PV.

Choose Storage in the navigation pane and click the PVCs tab. Click Create PVC in the upper right corner. In the dialog box displayed, configure the PVC 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 no underlying storage is available, select Dynamically provision to create a PVC, PV, and underlying storage on the console in cascading mode. 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. For details, see Using an Existing SFS File System Through a Static PV. In this example, select Dynamically provision.
Storage Classes	The storage class for SFS volumes is csi-nas.
Access Mode	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.
Encryption	Configure whether to encrypt underlying storage. If you select Enabled (key), an encryption key must be configured.

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.

Create an application.

In the navigation pane on the left, click Workloads. In the right pane, click the Deployments tab.

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 indicates the container path to which a data volume will be mounted. Do not mount the volume to a system directory such as / or /var/run. Otherwise, containers will be malfunctional. 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, causing 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 machine 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 is 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.

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.

(kubectl) Automatically Creating an SFS File System

Use kubectl to access the cluster.

Use StorageClass to dynamically create a PVC and PV.

Create the pvc-sfs-auto.yaml file.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-sfs-auto
  namespace: default
  annotations: 
    everest.io/crypt-key-id: <your_key_id>      # (Optional) ID of the key for encrypting file systems
    everest.io/crypt-alias: sfs/default         # (Optional) Key name. Mandatory for encrypting volumes.
    everest.io/crypt-domain-id: <your_domain_id>   # (Optional) ID of the tenant to which an encrypted volume belongs. Mandatory for encrypting volumes.
spec:
  accessModes:
    - ReadWriteMany             # The value must be ReadWriteMany for SFS.
  resources:
    requests:
      storage: 1Gi             # SFS volume capacity.
  storageClassName: csi-nas    # The storage class is SFS.

**Table 2** Key parameters
Parameter	Mandatory	Description
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.
everest.io/crypt-key-id	No	This parameter is mandatory when an SFS system is encrypted. Enter the encryption key ID selected during SFS system creation. You can use a custom key or the default key named sfs/default. To obtain a key ID, log in to the DEW console, locate the key to be encrypted, and copy the key ID.
everest.io/crypt-alias	No	Key name, which is mandatory when you create an encrypted volume. To obtain a key name, log in to the DEW console, locate the key to be encrypted, and copy the key name.
everest.io/crypt-domain-id	No	ID of the tenant to which the encrypted volume belongs. This parameter is mandatory for creating an encrypted volume. To obtain a tenant ID, hover the cursor over the username in the upper right corner of the ECS console, choose My Credentials, and copy the account ID.

Run the following command to create a PVC:
```
kubectl apply -f pvc-sfs-auto.yaml
```

Create an application.

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    # Volume name, which can be customized.
          persistentVolumeClaim:
            claimName: pvc-sfs-auto    # Name of the created PVC.

Run the following command to create a workload to which the SFS volume is mounted:
```
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

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.
Run the following command to create a file named static in the /data path:
```
kubectl exec web-demo-846b489584-mjhm9 --  touch /data/static
```
Run the following command to view the files in the /data path:
```
kubectl exec web-demo-846b489584-mjhm9 -- ls /data
```
Expected output:
```
static
```
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
```
  If the static file still exists, the data can be stored persistently.
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

You can also perform the operations listed in Table 3.

**Table 3** Related operations
Operation	Description	Procedure
Viewing events	You can view event names, event types, number of occurrences, Kubernetes events, first occurrence time, and last occurrence time of the PVC or PV.	Choose Storage in the navigation pane and click the PVCs or PVs tab. Click View Events in the Operation column of the target PVC or PV to view events generated within one hour (event data is retained for one hour).
Viewing a YAML file	You can view, copy, and download the YAML files of a PVC or PV.	Choose Storage in the navigation pane and click the PVCs or PVs tab. Click View YAML in the Operation column of the target PVC or PV to view or download the YAML.