Use NAS volumes for shared persistent storage - User Guide for Kubernetes Clusters| Alibaba Cloud Documentation Center

You can use an Apsara File Storage NAS (NAS) volume to persist data and share the data among multiple pods. This topic describes how to use a NAS file system to persist and share data.

Prerequisites

Create a managed Kubernetes cluster.
Connect to Kubernetes clusters by using kubectl.
A NAS file system is created in the NAS File System console. For more information, see Mount an NFS file system. The NAS file system and the cluster are deployed in the same zone.
A mount target is added to the NAS file system. For more information, see . The NAS file system and the cluster are deployed in the same virtual private cloud (VPC).

Background information

If a NAS file system is mounted on multiple pods, the data in the file system is shared among the pods. The application must be able to synchronize data across all pods when data modifications are made by multiple pods.

Scenarios:

Your application requires high disk I/O.
You need a storage service that offers higher read and write throughput than Object Storage Service (OSS).
You want to share files across hosts. For example, you want to use a NAS file system as a file server.

Procedure

Create a NAS file system and create a mount target.
Create a persistent volume (PV) and a persistent volume claim (PVC).

The following section describes how to create a PV and a PVC by using the FlexVolume plug-in provided by Alibaba Cloud and then mount a NAS file system.

Create a PV

Create a file named pv-nas.yaml.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nas
  labels:
    alicloud-pvname: pv-nas
spec:
  capacity:
    storage: 5Gi
  accessModes:
    - ReadWriteMany
  flexVolume:
    driver: "alicloud/nas"
    options:
      server: "***-**.cn-hangzhou.nas.aliyuncs.com"   #Replace the value with the mount target.
      path: "/k8s1"
      vers: "4.0"


Parameter	Description
`alicloud-pvname`	The name of the PV.
`server`	The mount target of the NAS file system. To obtain the mount target, log on to the NAS File System console. In the left-side navigation pane, click File System List, find the created file system, and then click Management in the Operations column. Click the Mounting Use tab and copy the mount address in the Mount Target column.
`path`	The mounted directory of the NAS file system. You can specify a subdirectory of a NAS file system. If no subdirectories exist, the system automatically creates a subdirectory.
`vers`	The version number of the Network File System (NFS) protocol. This parameter is optional. Valid values: 3 and 4.0. Default value: 3.
`mode`	The access permissions on the mounted directory. This parameter is optional. By default, this parameter is left empty. Note You are not allowed to grant permissions to access the root directory of a NAS file system. If you set the `mode` parameter for a NAS file system that stores a large amount of data, the process of mounting the NAS file system may be time-consuming or even fail. We recommend that you leave this parameter empty.

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

Expected result

Log on to the ACK console.
In the left-side navigation pane, click Clusters.
On the Clusters page, find the cluster that you want to manage, and click the name of the cluster or click Details in the Actions column.
In the left-side navigation pane of the details page, choose Volumes > Persistent Volumes. Verify that the newly created PV is displayed.

Create a PVC

When you create a PVC of the NAS type, set the selector parameter to configure how to select the PV to which the PVC is bound.

Create a file named pvc-nas.yaml.

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: pvc-nas
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 5Gi
  selector:
    matchLabels:
      alicloud-pvname: pv-nas

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

Expected result

Log on to the ACK console.
In the left-side navigation pane, click Clusters.
On the Clusters page, find the cluster that you want to manage, and click the name of the cluster or click Details in the Actions column.
In the left-side navigation pane of the details page, choose Volumes > Persistent Volume Claims. Verify that the newly created PVC is displayed.

Create an application

Create a file named nas.yaml.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nas-static
  labels:
    app: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
          - name: pvc-nas
            mountPath: "/data"
      volumes:
        - name: pvc-nas
          persistentVolumeClaim:
            claimName: pvc-nas

Run the following command to deploy an application:
```
kubectl create -f nas.yaml
```

Expected result

Log on to the ACK console.
In the left-side navigation pane, click Clusters.
On the Clusters page, find the cluster that you want to manage, and click the name of the cluster or click Applications in the Actions column.
In the left-side navigation pane of the cluster details page, choose Workloads > Deployments. Verify that the newly created application is displayed.

Verify data sharing

Run the following command to query the pods that run the application.

kubectl get pod

Expected output:

NAME                             READY   STATUS    RESTARTS   AGE
nas-static-f96b6b5d7-r****       1/1     Running   0          9m
nas-static-f96b6b5d7-w****       1/1     Running   0          9m

Run the following commands to query the files in the /data path:

kubectl exec nas-static-f96b6b5d7-r**** ls /data

Expected output:

kubectl exec nas-static-f96b6b5d7-w**** ls /data

Note The output indicates that no file exists in the /data path.

Run the following command to create a file named nas in the /data path of a pod:
```
kubectl exec nas-static-f96b6b5d7-r**** touch /data/nas
```
Query files in the pods.
Run the following command to query files in the /data path of one pod:
```
kubectl exec nas-static-f96b6b5d7-r**** ls /data
```
Expected output:
```
nas
```
Run the following command to query files in the /data path of the other pod:
```
kubectl exec nas-static-f96b6b5d7-w**** ls /data
```
Expected output:
```
nas
```
Note The file was created in the /data path of one of the pods. However, you can find the file in the /data path of both pods. This indicates that the pods share the NAS volume.

Verify data persistence

Run the following commands to delete all pods of the application:

kubectl delete pod nas-static-f96b6b5d7-r**** nas-static-f96b6b5d7-wthmb

Expected output:

pod "nas-static-f96b6b5d7-r****" deleted
pod "nas-static-f96b6b5d7-w****" deleted

Run the following command to view how the pods are deleted and recreated:

kubectl get pod -w -l app=nginx

Expected output:

NAME                             READY   STATUS              RESTARTS       AGE
nas-static-f96b6b5d7-r****       1/1     Running             0              27m
nas-static-f96b6b5d7-w****       1/1     Running             0              27m
nas-static-f96b6b5d7-r****       1/1     Terminating         0              28m
nas-static-f96b6b5d7-w****       0/1     Pending             0              0s
nas-static-f96b6b5d7-w****       0/1     Pending             0              0s
nas-static-f96b6b5d7-w****       0/1     ContainerCreating   0              0s
nas-static-f96b6b5d7-w****       1/1     Terminating         0              28m
nas-static-f96b6b5d7-n****       0/1     Pending             0              0s
nas-static-f96b6b5d7-n****       0/1     Pending             0              0s
nas-static-f96b6b5d7-n****       0/1     ContainerCreating   0              0s
nas-static-f96b6b5d7-r****       0/1     Terminating         0              28m
nas-static-f96b6b5d7-w****       0/1     Terminating         0              28m
nas-static-f96b6b5d7-r****       0/1     Terminating         0              28m
nas-static-f96b6b5d7-r****       0/1     Terminating         0              28m
nas-static-f96b6b5d7-w****       1/1     Running             0              10s
nas-static-f96b6b5d7-w****       0/1     Terminating         0              28m
nas-static-f96b6b5d7-w****       0/1     Terminating         0              28m
nas-static-f96b6b5d7-n****       1/1     Running             0              17s

Run the following command to query the newly created pods:

kubectl get pod

Expected output:

NAME                             READY   STATUS    RESTARTS   AGE
nas-static-f96b6b5d7-n****       1/1     Running   0          21s
nas-static-f96b6b5d7-w****       1/1     Running   0          21s

Query files in the pods.
Run the following command to query files in the /data path of one pod:
```
kubectl exec nas-static-f96b6b5d7-n**** ls /data
```
Expected output:
```
nas
```
Run the following command to query files in the /data path of the other pod:
```
kubectl exec nas-static-f96b6b5d7-w**** ls /data
```
Expected output:
```
nas
```
Note The nas file still exists. This indicates that data is persisted to the NAS volume.