Mount a statically provisioned NAS volume - Container Service for Kubernetes

Apsara File Storage NAS (NAS) is a distributed file system that supports shared access, elastic scaling, high reliability, and high performance. This topic describes how to mount a statically provisioned NAS volume, and how to enable persistent storage and shared storage by using a statically provisioned NAS volume.

Prerequisites

An ACK cluster is created. For more information, see Create an ACK managed 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, configure the encryption settings when you create the NAS file system.
A mount target is created for the NAS file system. For more information, see Manage mount targets.
The mount target and the cluster node to which you want to mount the NAS file system must belong to the same virtual private cloud (VPC).
A kubectl client is connected to the cluster. For more information, see Obtain the kubeconfig file of a cluster and use kubectl to connect to the cluster.

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.

Precautions

To mount an Extreme NAS file system, set the path parameter of the NAS volume to a subdirectory of /share. For example, you can specify the /share/path1 subdirectory when you mount an Extreme NAS file system to a pod.
If a NAS file system is mounted to multiple pods, the data in the file system is shared by the pods. In this case, the application must be able to synchronize data across the pods if the data in the NAS file system is modified by multiple pods.
Note You cannot grant permissions to access the / directory (root directory) of the NAS file system. The user account and user group to which the directory belongs cannot be modified.
Statically provisioned NAS volumes cannot be expanded.
If the securityContext.fsgroup parameter is set in the application template, kubelet performs the chmod or chown operation after the volume is mounted, which increases the time consumption.
Note For more information about how to speed up the mounting process when the securityContext.fsgroup parameter is set, For more information, see Why does it require a long time to mount a NAS volume?.

Mount a statically provisioned NAS volume in the console

Step 1: Create a PV

Log on to the ACK console.
In the left-side navigation pane of the ACK console, 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.
In the upper-right corner of the Persistent Volumes page, click Create.

In the Create PV dialog box, set the following parameters.


Parameter	Description
PV Type	You can select Cloud Disk, NAS, or OSS. In this example, NAS is selected.
Volume Name	The name of the PV that you want to create. The name must be unique in the cluster. In this example, pv-nas is used.
Volume Plug-in	You can select Flexvolume or CSI. In this example, CSI is selected.
Capacity	The capacity of the PV. A NAS file system provides unlimited capacity. This parameter does not limit the storage usage of the NAS file system but defines the capacity of the PV.
Access mode	You can select ReadWriteMany or ReadWriteOnce. Default value: ReadWriteMany.
Mount Target Domain Name	You can select Select Mount Target to select a mount target or select Custom to enter a mount target.
Show Advanced Options	Subdirectory: the subdirectory of the NAS file system that you want to mount. The subdirectory must start with a forward slash (/). After you set this parameter, the PV is mounted to the subdirectory. If the specified subdirectory does not exist, the system automatically creates the subdirectory in the NAS file system and mounts the subdirectory to the cluster. If you do not set this parameter, the root directory of the NAS file system is mounted. If you want to mount an Extreme NAS file system, the subdirectory must be under the /share directory. Version: the version of the PV.
Label	Add labels to the PV.

Click Create.

Step 2: Create a PVC

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

In the Create PVC dialog box, set the following parameters.


Parameter	Description
PVC Type	You can select Cloud Disk, NAS, or OSS. In this example, NAS is selected.
Name	The name of the persistent volume claim (PVC). The name must be unique in the cluster.
Allocation Mode	In this example, Existing Volumes is selected. Note If no PV is created, you can set Allocation Mode to Create Volume and set the required parameters to create a PV. For more information, see Create a PV.
Existing Volumes	Click Select PV. Find the PV that you want to use and click Select in the Actions column.
Capacity	The capacity claimed by the PVC. Note The capacity claimed by the PVC cannot exceed the capacity of the PV that is bound to the PVC.

Click Create.
After the PVC is created, you can view the PVC in the PVCs list. The PVC is bound to the corresponding PV.

Step 3: Create an application

In the left-side navigation pane of the details page, choose Workloads > Deployments.
In the upper-right corner of the Deployments page, click Create from Image.
Configure the application parameters.
This example shows how to configure the volume parameters. For more information about other parameters, see Create a stateless application by using a Deployment.
You can add local volumes and cloud volumes.
- Add Local Storage: You can select HostPath, ConfigMap, Secret, or EmptyDir from the PV Type drop-down list. Then, set the Mount Source and Container Path parameters to mount the volume to a container path. For more information, see Volumes.
- Add PVC: You can add cloud volumes.
In this example, a NAS volume is mounted to the /tmp path in the container.
Set other parameters and click Create.
After the application is created, you can use the volume to store application data.

Mount a statically provisioned NAS volume by using kubectl

Run the following command to create a statically provisioned PV:

kubectl create -f pv-nas.yaml

The following YAML template provides an example on how to create 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   # It must be consistent with pv name.
    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 that you want to add to the PV.
storage	The capacity of the NAS volume.
accessModes	The access mode of the PV.
driver	The type of driver. In this example, the parameter is set to `nasplugin.csi.alibabacloud.com`. This indicates that the NAS Container Storage Interface (CSI) plug-in provided by Alibaba Cloud is used.
volumeHandle	The unique identifier of the PV. It must be consistent with pv name. If multiple PVs are used, the identifier of each PV must be unique.
server	The mount target of the NAS file system.
path	The subdirectory of the NAS file system that you want to mount. If you want to mount an Extreme NAS file system, the subdirectory must be under the /share directory.
vers	The version of the Network File System (NFS) protocol. We recommend that you use NFSv3. Extreme NAS file systems support only NFSv3.

Run the following command to create a PVC used for static provisioning:

When you create a PVC of the NAS type, set the selector parameter to specify how to select a PV and bind it to the PVC.

kubectl create -f pvc-nas.yaml

The following YAML template provides an example on how to create a PVC used for static provisioning:

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 of the PVC.
storage	The capacity claimed by the PVC. The claimed capacity cannot exceed the capacity of the PV that is bound to the PVC.
matchLabels	The labels are used to select a PV and bind it to the PVC.

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

kubectl create -f nas.yaml

The following YAML template provides an example of the nas.yaml file that is used to create 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: nginx
        ports:
        - containerPort: 80
        volumeMounts:
          - name: pvc-nas
            mountPath: "/data"
      volumes:
        - name: pvc-nas
          persistentVolumeClaim:
            claimName: pvc-nas


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

Run the following command to query the pods that run the 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

Verify that the NAS file system can be used to persist data

Query the pods that run the application and the files in the mounted NAS file system.
1. Run the following command to query the pods that run the 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 query files in the /data path of a pod. The pod nas-static-5b5cdb85f6-n**** is used as an example:
```
kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
```
  No output is returned. This indicates that no file is stored in the /data path.
Run the following command to create a file named nas in the /data path of the pod nas-static-5b5cdb85f6-n****:
```
kubectl exec nas-static-5b5cdb85f6-n**** -- touch /data/nas
```
Run the following command to query files in the /data path of the pod nas-static-5b5cdb85f6-n****:
```
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****

Open another command-line interface (CLI) and run the following command to view how the pod is deleted and recreated:
```
kubectl get pod -w -l app=nginx
```
Verify that the file still exists after the pod is deleted.
1. Run the following command to query the name of the recreated pod:
```
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 query files in the /data path of the pod nas-static-5b5cdb85f6-n****:
```
kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
```
  Expected output:
```
nas
```
  The nas file still exists in the /data path. This indicates that data is persisted to the NAS file system.

Verify that data in the NAS file system can be shared across pods

Query the pods that run the application and the files in the mounted NAS file system.

Run the following command to query the pods that run the 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

Run the following command to query files in the /data path of each pod:

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 a pod:
```
 kubectl exec nas-static-5b5cdb85f6-n**** -- touch /data/nas
```
Run the following command to query files in the /data path of each pod:
1. Run the following command to query files in the /data path of the pod nas-static-5b5cdb85f6-n****:
```
kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
```
  Expected output:
```
nas
```
2. Run the following command to query files in the /data path of the pod nas-static-c5bb4746c-4****:
```
kubectl exec nas-static-c5bb4746c-4**** -- ls /data
```
  Expected output:
```
nas
```
  When you create a file in the /data path of one pod, you can also find the file in the /data path of the other pod. This indicates that data in the NAS file system is shared by the two pods.