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 and implement data persistence and sharing in workloads.

Prerequisites

You have created a cluster and installed the CSI add-on (everest) in the cluster.
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 an SFS file system that is in the same VPC as the cluster.

Constraints

Multiple PVs can use the same SFS or SFS Turbo file system with the following restrictions:
- If multiple PVCs/PVs use the same underlying SFS or SFS Turbo file system, when you attempt to mount these PVCs/PVs to the same pod, all PVCs cannot be mounted to the pod and the pod startup fails. This is because the volumeHandle values of these PVs are the same.
- 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.

(kubectl) Using an Existing SFS File System

Use kubectl to connect to 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 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: disk.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               # Storage class name. csi-nas indicates that SFS Capacity-Oriented is used.
  mountOptions: []                         # Mount options.

**Table 1** Key parameters
Parameter	Mandatory	Description
everest.io/reclaim-policy: retain-volume-only	No	Optional. Currently, only retain-volume-only is supported. This field 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 console, choose Service List > Storage > Scalable File Service, and select SFS Turbo. 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 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 avoid cascading deletion of underlying volumes. Delete: If everest.io/reclaim-policy is not specified, both the PV and SFS volume are deleted when a PVC is deleted. If everest.io/reclaim-policy is set to retain-volume-only set, when a PVC is deleted, the PV is deleted but the SFS volume resources are 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 status and cannot be bound to the 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.

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 an application 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 applications 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 another pods, 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 from the navigation pane, and click the PersistentVolumeClaims (PVCs) or PersistentVolumes (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 from the navigation pane, and click the PersistentVolumeClaims (PVCs) or PersistentVolumes (PVs) tab. Click View YAML in the Operation column of the target PVC or PV to view or download the YAML.