Mount a statically provisioned NAS volume - Container Service for Kubernetes

A NAS volume is a distributed file system that provides shared access, scalability, high reliability, and high performance. This topic describes how to use a statically provisioned Alibaba Cloud NAS volume to implement persistent and shared storage.

Prerequisites

An ACK Serverless cluster is created. For more information, see Create an ACK Serverless cluster.
A NAS file system is created. For more information, see Create a file system.
If you want to encrypt data in a NAS volume, you must configure the encryption type when you create the NAS file system.
A NAS mount target is created. For more information, see Manage mount targets.
The NAS mount target must be in the same VPC as the cluster nodes.
You have connected to the cluster using kubectl. For more information, see Obtain the kubeconfig file of a cluster and use kubectl to connect to the cluster.

Scenarios

Applications that have high requirements for disk I/O.
You can implement file sharing across hosts. For example, you can use a NAS volume as a file server.

Considerations

When you use an Extreme NAS file system, the path of the volume must be a subdirectory of /share. For example, you can set the subdirectory of the NAS file system that is mounted to a pod to /share/path1.
A NAS file system can be mounted to multiple pods at the same time. In this case, the pods may modify the same data. Your application must be able to synchronize data.
Note
You cannot modify the permissions, owner, or group of the / directory of a NAS file system.
If you set the securityContext.fsgroup parameter in the application template, Kubelet runs the chmod or chown operation after the volume is mounted. This prolongs the mount time.
Note
If you have set the securityContext.fsgroup parameter and want to reduce the mount time, see The mount time of a NAS volume is prolonged.

Use a statically provisioned NAS volume in the console

Step 1: Create a Persistent Volume (PV)

Log on to the ACK console. In the left 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. The details page of the cluster appears.
In the left-side navigation pane of the cluster details page, choose Volumes > Persistent Volumes.
On the Persistent Volumes page, click Create in the upper-left corner.

In the Create PV dialog box, set the parameters.

Parameter		Description
PV Type		In this example, select NAS.
Name		The name of the PV. The name must be unique in the cluster. In this example, pv-nas is used.
Capacity		The capacity of the PV. Note that NAS file systems do not have a capacity limit. This parameter specifies the capacity of the PV, not the capacity limit of the NAS file system.
Access Mode		Select ReadWriteMany or ReadWriteOnce. The default value is ReadWriteMany.
Mount Target Domain Name		You can Select Mount Target or specify a Custom mount target as the mount address for the cluster to access the NAS file system.
Advanced Options (Optional)	Mount Path	Subdirectory in the NAS file system to mount. If not set, defaults to root (`/`for General-purpose NAS, `/share` for Extreme NAS). If the directory doesn't exist, it will be created. Note For Extreme NAS, paths must start with `/share`, such as `/share/data`.
	Reclaim Policy	The default value is Retain. This indicates that when a PVC is deleted, the related PV and NAS file system are retained and can only be manually deleted.
	Mount Options	NAS mount parameter, including NFS protocol version. We recommend using NFS v3 protocol, because Extreme NAS only supports NFS v3. For more information about the NFS protocol, see NFS protocol.
Label		Add labels to the PV.

After you set the parameters, click OK.

Step 2: Create a Persistent Volume Claim (PVC)

In the left-side navigation pane of the details page, choose Volumes > Persistent Volume Claims.
On the Persistent Volume Claims page, click Create in the upper-left corner.

In the Create PVC dialog box, set the parameters.

Parameter	Description
PVC Type	In this example, select NAS.
Name	The name of the PVC. The name must be unique in the cluster.
Allocation Mode	Select Existing Volumes. Note If no PV is created, you can set Allocation Mode to Create Volume and set the parameters to create a PV. For more information, see Create a PV.
Existing Volumes	Click Select PV, find the target PV, and then click Select in the Actions column.
Capacity	The capacity of the PV. Note The capacity claimed by the PVC cannot exceed the capacity of the PV that is bound to the PVC.

Click OK.
After the PVC is created, you can view it in the list. The status of the PVC changes to Bound, which indicates that it is bound to the corresponding PV.

Step 3: Create an application

In the navigation pane on the left of the cluster details page, go to Workloads > Deployments.
On the Deployments page, click Create From Image.

Configure the parameters of the application. After doing so, click Create.

The following table describes the key parameters. Use default settings for other parameters. For more information, see Create a stateless application using a Deployment.

Section	Parameter	Description	Example
Basic Information	Name	Enter a custom name for the Deployment. The name must meet the format requirements displayed in the console.	nas-test
Basic Information	Replicas	Number of pod replicas.	2
Container	Image Name	Container image.	anolis-registry.cn-zhangjiakou.cr.aliyuncs.com/openanolis/nginx:1.14.1-8.6
	Required Resources	CPU and memory.	0.25 Core, 512 MiB
	Volume	Click Add PVC and configure the parameters. Mount Source: Select the PVC that you created. Container Path: Specify the container path to which you want to mount the NAS file system.	Mount Source: pvc-nas Container Path: /data

View the application deployment status.
1. On the Deployments page, click the name of the application.
2. On the Pods tab, confirm pods are in the Running state.

Use a statically provisioned NAS volume using kubectl

Run the following command to create a statically provisioned PV.

kubectl create -f pv-nas.yaml

The following code provides a sample YAML file for creating a statically provisioned PV.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nas
  labels:
    alicloud-pvname: pv-nas
spec:
  capacity:
    storage: 5Gi
  accessModes:
    - ReadWriteMany
  csi:
    driver: nasplugin.csi.alibabacloud.com
    volumeHandle: pv-nas
    volumeAttributes:
      server: "2564f4****-ysu87.cn-shenzhen.nas.aliyuncs.com"
      path: "/csi"
  mountOptions:
  - nolock,tcp,noresvport
  - vers=3

Parameter	Description
name	The name of the PV.
labels	The labels of the PV.
storage	The available capacity of the NAS file system.
accessModes	The access mode.
driver	The type of the driver. In this example, the value is `nasplugin.csi.alibabacloud.com`, which indicates that the Alibaba Cloud NAS CSI plug-in is used.
volumeHandle	The unique ID of the PV. If you want to use multiple PVs at the same time, the value of this parameter must be unique for each PV.
server	The NAS mount target.
path	The subdirectory to mount. For an Extreme NAS file system, the subdirectory must be a subdirectory of /share.
vers	The version number of the NFS protocol that is used to mount the NAS volume. We recommend that you use v3. Extreme NAS file systems support only v3.

Run the following command to create a statically provisioned PVC.

Create a PVC for the NAS file system. Use the selector field to filter PVs and bind the PVC to a specific PV.

kubectl create -f pvc-nas.yaml

The following code provides a sample YAML file for creating a statically provisioned PVC.

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

Parameter	Description
name	The name of the PVC.
accessModes	The access mode.
storage	The capacity requested by the application. The value cannot be greater than the total capacity of the PV.
matchLabels	The labels of the PV to associate.

Run the following command to create an application named nas-static and mount the PVC.

kubectl create -f nas.yaml

The following code provides a sample nas.yaml file for creating the nas-static application.

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: registry.cn-hangzhou.aliyuncs.com/acs-sample/nginx:latest
        ports:
        - containerPort: 80
        volumeMounts:
          - name: pvc-nas
            mountPath: "/data"
      volumes:
        - name: pvc-nas
          persistentVolumeClaim:
            claimName: pvc-nas

Parameter	Description
mountPath	The path to which the NAS volume is mounted in the container.
claimName	The name of the PVC to bind.

Run the following command to view pod information.

kubectl get pod

Expected output:

NAME                          READY   STATUS    RESTARTS   AGE
nas-static-5b5cdb85f6-n****   1/1     Running   0          32s
nas-static-c5bb4746c-4****    1/1     Running   0          32s

Verify the persistence of the NAS volume

View the deployed application and NAS files.
1. Run the following command to view the names of the pods for the deployed application.
```
kubectl get pod 
```
  Expected output:
```
NAME                          READY   STATUS    RESTARTS   AGE
nas-static-5b5cdb85f6-n****   1/1     Running   0          32s
nas-static-c5bb4746c-4****    1/1     Running   0          32s
```
2. Run the following command to view the files in the /data path of one of the application pods. This topic uses the pod named nas-static-5b5cdb85f6-n**** as an example.
```
kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
```
  The command returns no output, which indicates that no file exists in the /data path.
Run the following command to create a file named nas in the /data path of the nas-static-5b5cdb85f6-n**** pod.
```
kubectl exec nas-static-5b5cdb85f6-n**** -- touch /data/nas
```
Run the following command to view the files in the /data path of the nas-static-5b5cdb85f6-n**** pod.
```
kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
```
Expected output:
```
nas
```

Run the following command to delete the pod.

kubectl delete pod nas-static-5b5cdb85f6-n****

In another window, run the following command to monitor the deletion of the pod and the creation of a new pod by Kubernetes.
```
kubectl get pod -w -l app=nginx
```
Verify that the file created in the NAS volume still exists after the pod is deleted.
1. Run the following command to view the name of the pod that is recreated by Kubernetes.
```
kubectl get pod
```
  Expected output:
```
NAME                                READY   STATUS    RESTARTS   AGE
nas-static-5b5cdb85f6-n****   1/1     Running   0          32s
nas-static-c5bb4746c-4****    1/1     Running   0          32s
```
2. Run the following command to view the files in the /data path of the nas-static-5b5cdb85f6-n**** pod.
```
kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
```
  Expected output:
```
nas
```
  The nas file still exists, which indicates that the data in the NAS volume is persistent.

Verify the shared storage of the NAS volume

View the pods where the application is deployed and the NAS files.

Run the following command to view the names of the pods where the application is deployed.

kubectl get pod

Expected output:

NAME                          READY   STATUS    RESTARTS   AGE
nas-static-5b5cdb85f6-n****   1/1     Running   0          32s
nas-static-c5bb4746c-4****    1/1     Running   0          32s

Run the following command to view the files in the /data path of the two pods.

kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
kubectl exec nas-static-c5bb4746c-4**** -- ls /data

Run the following command to create a file named nas in the /data path of one of the pods.
```
 kubectl exec nas-static-5b5cdb85f6-n**** -- touch /data/nas
```
Run the following command to view the files in the /data path of the two pods.
1. Run the following command to view the files in the /data path of the pod named nas-static-5b5cdb85f6-n****.
```
kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
```
  Expected output:
```
nas
```
2. Run the following command to view the files in the /data path of the pod named nas-static-c5bb4746c-4****.
```
kubectl exec nas-static-c5bb4746c-4**** -- ls /data
```
  Expected output:
```
nas
```
  If the file created in the /data path of one pod also exists in the /data path of the other pod, it indicates that the two pods share the same NAS volume.