This topic describes the common scenarios of static disks and how to use static disks to create persistent volumes (PVs) for stateful services.

Prerequisites

Background information

Scenarios:
  • Create applications that require high disk I/O and do not require shared data. For example, MySQL, Redis, and other data storage services.
  • Collect logs at high speeds.
  • Store data in a way that is independent of the lifetime of a pod.

Before you use static disks, make sure that you have purchased disks.

To use a static disk, manually create a PV and a persistent volume claim (PVC). For more information, see Use static volumes.

Limits

  • Disks provided by Alibaba Cloud cannot be shared. Each disk can be mounted to only one pod at a time.
  • Disks can only be mounted to nodes that are located in the same zone.

Create a PV

  1. Add the following content to the pv-static.yaml file: 
    apiVersion: v1
kind: PersistentVolume
metadata:
  name: <your-disk-id>
  labels:
    alicloud-pvname: <your-disk-id>
    failure-domain.beta.kubernetes.io/zone: <your-zone>
    failure-domain.beta.kubernetes.io/region: <your-region>
spec:
  capacity:
    storage: 20Gi
  accessModes:
    - ReadWriteOnce
  flexVolume:
    driver: "alicloud/disk"
    fsType: "ext4"
    options:
      volumeId: "<your-disk-id>"
    Note
    • alicloud-pvname: <your-disk-id>: the name of the PV. Set the value to the disk ID.
    • failure-domain.beta.kubernetes.io/zone: <your-zone>: the zone where the disk is located. For example, cn-hangzhou-b.
    • failure-domain.beta.kubernetes.io/region: <your-region>: the region where the disk is located. For example, cn-hangzhou.

    If your cluster is deployed across multiple zones, specify the failure-domain.beta.kubernetes.io/zone and failure-domain.beta.kubernetes.io/region parameters to ensure that your pod is scheduled to the zone where the disk is located.

  2. Run the following command to create a PV:
    kubectl create -f pv-static.yaml

Expected results:

In the left-side navigation pane of the details page of the cluster, click Persistent Volumes. On the Persistent Volumes tab, view the newly created PV.

Create a PVC

  1. Add the following content to the pvc-static.yaml file: 
    kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: pvc-disk
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
  selector:
    matchLabels:
      alicloud-pvname: <your-disk-id>
  2. Run the following command to create a PVC: 
    kubectl create -f pvc-static.yaml

Expected results:

In the left-side navigation pane of the details page of the cluster, click Persistent Volumes. On the Persistent Volume Claims tab, view the newly created PVC.

Create an application

  1. Add the following content to the static.yaml file: 
    apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-static
  labels:
    app: nginx
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        volumeMounts:
          - name: disk-pvc
            mountPath: "/data"
      volumes:
        - name: disk-pvc
          persistentVolumeClaim:
            claimName: pvc-disk
  2. Run the following command to create an application:
    kubectl create -f static.yaml

Expected results:

In the left-side navigation pane of the details page of the cluster, click Workload. On the Deployments tab, view the application.

Use static disks for persistent storage

  1. Run the following command to query the pod that runs the application:
    kubectl get pod | grep static

    The following command output appears:

    nginx-static-78c7dcb9d7-g****   2/2     Running     0          32s
  2. Run the following command to check whether a new disk is mounted to the /data path:
    kubectl exec nginx-static-78c7dcb9d7-g**** df | grep data

    The following command output appears:

    /dev/vdf        20511312    45080  20449848   1% /data
  3. Run the following command to query the files in the /data path: 
    kubectl exec nginx-static-78c7dcb9d7-g**** ls /data

    The following command output appears:

    lost+found
  4. Run the following command to create file static in the /data path:
    kubectl exec nginx-static-78c7dcb9d7-g**** touch /data/static
  5. Run the following command to query the files in the /data path:
    kubectl exec nginx-static-78c7dcb9d7-g**** ls /data

    The following command output appears:

    static
lost+found
  6. Run the following command to delete pod nginx-static-78c7dcb9d7-g****:
    kubectl delete pod nginx-static-78c7dcb9d7-g****

    The following command output appears:

    pod "nginx-static-78c7dcb9d7-g****" deleted
  7. Open another kubectl CLI and run the following command to query how the pod is deleted and a new pod is created: 
    kubectl get pod -w -l app=nginx

    The following command output appears:

    NAME                            READY   STATUS            RESTARTS   AGE
nginx-static-78c7dcb9d7-g****   2/2     Running           0          50s
nginx-static-78c7dcb9d7-g****   2/2     Terminating       0          72s
nginx-static-78c7dcb9d7-h****   0/2     Pending           0          0s
nginx-static-78c7dcb9d7-h****   0/2     Pending           0          0s
nginx-static-78c7dcb9d7-h****   0/2     Init:0/1          0          0s
nginx-static-78c7dcb9d7-g****   0/2     Terminating       0          73s
nginx-static-78c7dcb9d7-h****   0/2     Init:0/1          0          5s
nginx-static-78c7dcb9d7-g****   0/2     Terminating       0          78s
nginx-static-78c7dcb9d7-g****   0/2     Terminating       0          78s
nginx-static-78c7dcb9d7-h****   0/2     PodInitializing   0          6s
nginx-static-78c7dcb9d7-h****   2/2     Running           0          8s
  8. Run the following command to query the new pod: 
    kubectl get pod

    The following command output appears:

    NAME                            READY   STATUS      RESTARTS   AGE
nginx-static-78c7dcb9d7-h****   2/2     Running     0          14s
  9. Run the following command to verify that file static exists in the /data path. This indicates that data in the static disk is persistently stored.
    kubectl exec nginx-static-78c7dcb9d7-h6brd ls /data

    The following command output appears:

    static
lost+found