Using an Existing SFS File System Through a Static PV

SFS is a network-attached storage (NAS) that provides shared, scalable, and high-performance file storage. It applies to large-capacity expansion and cost-sensitive services. This section describes how to use an existing SFS file system to statically create PVs and PVCs for data persistence and sharing in workloads.

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.

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.

Using an Existing SFS File System Through kubectl

Use kubectl to access the cluster.

Create a PV.

Create the pv-sfs.yaml file.

SFS Capacity-Oriented:

apiVersion: v1
kind: PersistentVolume
metadata:
  annotations:
    pv.kubernetes.io/provisioned-by: everest-csi-provisioner
    everest.io/reclaim-policy: retain-volume-only      # (Optional) The underlying volume is retained when the PV is deleted.
  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>   # SFS Capacity-Oriented volume ID
    volumeAttributes:
      everest.io/share-export-location: <your_location>  # Shared path of the SFS volume
      storage.kubernetes.io/csiProvisionerIdentity: everest-csi-provisioner
  persistentVolumeReclaimPolicy: Retain    # Reclaim policy
  storageClassName: csi-nas               # StorageClass name. csi-nas indicates that SFS Capacity-Oriented is used.
  mountOptions: []                         # Mount options

**Table 1** Key parameters
Parameter	Mandatory	Description
everest.io/reclaim-policy	No	Only retain-volume-only is supported. This parameter is valid only when the Everest version is 1.2.9 or later and the reclaim policy is Delete. If the reclaim policy is Delete and the current 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 Capacity-Oriented volume is used, enter the volume ID. Log in to the CCE console, choose Service List > Storage > Scalable File Service, and select SFS Capacity-Oriented. In the list, click the name of the target SFS file system. On the details page, copy the content following ID.
everest.io/share-export-location	Yes	Shared path of the file system. For an SFS Capacity-Oriented file system, log in to the CCE console, choose Service List > Storage > Scalable File Service, and obtain the shared path from the Mount Address column.
mountOptions	Yes	Mount options. If 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	A reclaim policy is supported when the cluster version is or later than 1.19.10 and the Everest version is or later than 1.2.9. 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. Retain: When a PVC is deleted, both the PV and underlying storage resources will be retained. You need to manually delete these resources. After the PVC is deleted, the PV is in the Released state and cannot be bound to a PVC again. Delete: When a PVC is deleted, its PV will also be deleted.
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.

Run the following command to create a PV:
```
kubectl apply -f pv-sfs.yaml
```

Create a PVC.

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-nas     # Storage class name, which must be the same as the PV's storage class. 
  volumeName: pv-sfs    # PV name

**Table 2** 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 1.

Run the following command to create a PVC:
```
kubectl apply -f pvc-sfs.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    # 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 check 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
```
  The static file is retained, indicating that the data in the file system 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	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. In the right pane, 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 (events are retained for one hour).
Viewing a YAML file	View, copy, or download the YAML file of a PVC or PV.	Choose Storage in the navigation pane. In the right pane, 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.