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Container Service for Kubernetes:Mount a statically provisioned NAS volume

Last Updated:Aug 28, 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

  • A 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, 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 your cluster. For more information, see Connect to an ACK cluster by using kubectl.

Scenarios

  • Your application requires high disk I/O.

  • 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.

  • If the securityContext.fsgroup parameter is set in the application template, kubelet performs the chmod or chown operation after the volume is mounted. This increases the mounting time.

    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 or NAS. In this example, NAS is selected.

    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

    Select CSI.

    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. 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, configure the required parameters.

    Parameter

    Description

    PVC Type

    You can select Cloud Disk or NAS. 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 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. volume

  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. 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
        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. 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.

  2. 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.

  3. 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.

  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 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.

  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 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
  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 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 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.