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Container Service for Kubernetes:Mount a statically provisioned NAS volume

Last Updated:Dec 07, 2023

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

Use 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.

Usage notes

  • 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, the 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, 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

  1. Log on to the ACK console.

  2. In the left-side navigation pane of the ACK console, click Clusters.

  3. 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.

  4. In the left-side navigation pane of the cluster details page, choose Volumes > Persistent Volumes.

  5. In the upper-right corner of the Persistent Volumes page, click Create.

  6. In the Create PV dialog box, configure 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.

  7. After you complete the configuration, click Create.

Step 2: Create a PVC

  1. In the left-side navigation pane of the details page, choose Volumes > Persistent Volume Claims.

  2. In the upper-right corner of the Persistent Volume Claims page, click Create.

  3. 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.

  4. 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

  1. In the left-side navigation pane of the details page, choose Workloads > Deployments.

  2. In the upper-right corner of the Deployments page, click Create from Image.

  3. 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.

  4. 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

  1. Create a statically provisioned PV.

    1. Create a file named pv-nas.yaml and copy the following content into the file:

      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   # Specify the name of the PV. 
          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 the storage driver that is used to provision the volume. In this example, the parameter is set to nasplugin.csi.alibabacloud.com. This indicates that the CSI plug-in provided by Alibaba Cloud is used.

      volumeHandle

      The unique identifier of the PV. Enter the name of the PV. If multiple PVs are used, the identifier of each PV must be unique.

      server

      The mount target of the NAS file system.

      Important

      Replace the value with the domain name of a mount target. For more information about how to view the domain name of a mount target, see View the domain name of a mount target.

      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.

    2. Run the following command to create a statically provisioned PV:

      kubectl create -f pv-nas.yaml
  2. Create a statically provisioned PVC.

    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.

    1. Create a file named pvc-nas.yaml and copy the following content into the file:

      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.

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

      kubectl create -f pvc-nas.yaml
  3. Deploy an application named nas-static and associate the PVC with the application.

    1. 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.

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

      kubectl create -f nas.yaml
  4. 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

  1. Query the deployed application and the files in the mounted NAS file system.

    1. Run the following command to query the name of 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 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 exists in the /data path.

  2. 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
  3. 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
  4. Run the following command to delete the pod:

    kubectl delete pod nas-static-5b5cdb85f6-n****
  5. Open another CLI and run the following command to view how the pod is deleted and recreated:

    kubectl get pod -w -l app=nginx
  6. 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

  1. Query the pods that are created for the application and the files in the mounted NAS file system.

    1. Run the following command to query the pods that are created for 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 each pod:

      kubectl exec nas-static-5b5cdb85f6-n**** -- ls /data
      kubectl exec nas-static-c5bb4746c-4**** -- ls /data
  2. 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
  3. 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.