Mount a NAS file system to store data of a stateful application - User Guide for Kubernetes Clusters| Alibaba Cloud Documentation Center

This topic describes the scenarios where you can mount an Apsara File Storage NAS (NAS) file system to pods and how to mount a NAS file system. After you mount a NAS file system to multiple pods, the pods can share data with each other.

Prerequisites

Create a managed Kubernetes cluster.
Use kubectl to connect to an ACK cluster.
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 your Kubernetes cluster must be deployed in the same zone.
A mount target is added to the NAS file system. For more information, see Mount an SMB file system on Windows. Make sure that the NAS file system and your Kubernetes cluster are connected to the same virtual private cloud (VPC).

Background information

If a NAS file system is mounted to multiple pods, data in the file system is shared by the pods. The application must be capable of automatically synchronizing application data across pods.

Note You are not allowed to grant permissions to access /directory (root directory) of the NAS file system. The user account and user group to which the directory belongs cannot be modified.

Scenarios

You want to run applications that require high disk I/O throughput.
You need a storage service whose read and write throughput is higher 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 add a mount target to it.
Manually create a persistent volume (PV) and a persistent volume claim (PVC).

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

Create a PV

Create a pv-nas.yaml file.

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 view the mount target, log on to the NAS File System console. Click File System List in the left-side navigation pane, find the file system, and then click Management in the Operations column. Click the Mounting Use tab and view the mount address in the Mount Target column.
`path`	The mount 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 mount 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 results:

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. Then, click the name of the cluster or click Details in the Actions column.
In the left-side pane of the details page, click Volumes.
Click the Persistent Volumes tab to view the PV that you created.

Create a PVC

Before you create a PVC for a NAS file system, you must set the selector parameter to specify the PV with which the PVC is associated.

Create a pvc-nas.yaml file.

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 results:

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. Then, click the name of the cluster or click Details in the Actions column.
In the left-side pane of the details page, click Volumes.
Click the Persistent Volume Claims tab to view the PVC that you created.

Deploy an application

Create a nas.yaml file.

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 results:

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. Then, click the name of the cluster or click Applications in the Actions column.
In the left-side navigation pane of the details page, click Workloads.
On the page that appears, click the Deployments tab to view the application that you deployed.

Verify that the NAS file system is shared by pods

Run the following command to query the pods of the application.

kubectl get pod

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 view files in the /data path:

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

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

Note No files are found in the /data path.

Run the following command to create the nas file in the /data path of a pod:
```
kubectl exec nas-static-f96b6b5d7-r**** touch /data/nas
```
Run the following commands to view files in the /data path:
```
kubectl exec nas-static-f96b6b5d7-r**** ls /data
```
```
nas
```
```
kubectl exec nas-static-f96b6b5d7-w**** ls /data
```
```
nas
```
Note Create a file in the /data path of a pod. Then, you can find the file in the same path (/data) on other pods. This indicates that these pods share the NAS file system.

Verify that data in the NAS file system is persisted.

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

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

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

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 view the names of the recreated pods:

kubectl get pod

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

Run the following commands to view files in the /data path:
```
kubectl exec nas-static-f96b6b5d7-n**** ls /data
```
```
nas
```
```
kubectl exec nas-static-f96b6b5d7-w**** ls /data
```
```
nas
```
Note The nas file still exists. This indicates that data is persisted to the NAS file system.