How to use a statically provisioned cloud disk volume for persistent storage-Container Service for Kubernetes(ACK)-阿里云帮助中心

When a container in a stateful service fails, its data can be lost. Persistent storage prevents this data loss. This topic explains how to use a statically provisioned cloud disk volume for persistent storage.

Prerequisites

Complete the following tasks:

Background information

Common use cases for cloud disks include:

Data storage services that require high disk I/O and do not require data sharing, such as MySQL and Redis.
High-speed log writes.
Persisting data beyond a pod's lifecycle.

If you have an existing cloud disk, use a statically provisioned volume.

To use a statically provisioned cloud disk volume, you must manually create a Persistent Volume (PV) and a Persistent Volume Claim (PVC). For more information, see Use a statically provisioned cloud disk volume.

Limits

Cloud disks are not shared and can be mounted to only one pod at a time.
A cloud disk can be mounted only to a node in the same zone.

Create a PV

Create a file named pv-static.yaml.
```
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, which must be the same as your cloud disk ID.
- failure-domain.beta.kubernetes.io/zone: <your-zone>: The zone where the cloud disk is located. For example, cn-hangzhou-b.
- failure-domain.beta.kubernetes.io/region: <your-region>: The region where the cloud disk is located. For example, cn-hangzhou.
If your cluster spans multiple zones, you must specify failure-domain.beta.kubernetes.io/zone and failure-domain.beta.kubernetes.io/region. This ensures pods are scheduled to the same zone as the cloud disk.
Run the following command to create the PV.
```
kubectl create -f pv-static.yaml
```
Verification Result
1. Log on to the Container Service Management Console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, click the name of the target cluster, or click Details in the Actions column.
4. In the left-side navigation pane of the cluster management page, choose Volumes > Persistent Volumes. You can view the newly created PV in the list. The capacity is 20Gi, the access mode is ReadWriteOnce, the reclaim policy is Retain, and the status is Available. The PV will be bound to the Persistent Volume Claim pvc-disk in the default namespace. The Actions column provides options to Manage Tags, View YAML, and Delete.

Create a PVC

Create a file named pvc-static.yaml.

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: pvc-disk
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
  selector:
    matchLabels:
      alicloud-pvname: <your-disk-id>

Run the following command to create the PVC.
```
kubectl create -f pvc-static.yaml
```
Verification Result
1. Log on to the Container Service Management Console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, click the name of the target cluster, or click Details in the Actions column.
4. In the left-side navigation pane of the cluster management page, choose Volumes > Persistent Volume Claims.
5. On the Persistent Volume Claims page, you can view the PVC you created.

Create an application

Create a file named static.yaml.

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

Run the following command to create the application.
```
kubectl create -f static.yaml
```
Verification Result
1. Log on to the Container Service Management Console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, click the name of the target cluster, or click Details in the Actions column.
4. In the left-side navigation pane of the cluster management page, choose Workloads > Deployments.
5. On the Deployments page, you can view the application you created.

Verify data persistence

Run the following command to get the application pod's name.

kubectl get pod | grep static

Expected output:

nginx-static-78c7dcb9d7-g****   2/2     Running     0          32s

Run the following command to verify that the cloud disk is mounted to the /data path.

kubectl exec nginx-static-78c7dcb9d7-g**** -- df | grep data

Expected output:

/dev/vdf        20511312    45080  20449848   1% /data

Run the following command to list the files in the /data path.
```
kubectl exec nginx-static-78c7dcb9d7-g**** -- ls /data
```
Expected output:
```
lost+found
```
Run the following command to create a file named static in the /data path.
```
kubectl exec nginx-static-78c7dcb9d7-g**** -- touch /data/static
```
Run the following command to list the files in the /data path.
```
kubectl exec nginx-static-78c7dcb9d7-g**** -- ls /data
```
Expected output:
```
static
lost+found
```
Run the following command to delete the pod named nginx-static-78c7dcb9d7-g****.
```
kubectl delete pod nginx-static-78c7dcb9d7-g****
```
Expected output:
```
pod "nginx-static-78c7dcb9d7-g****" deleted
```

In a separate terminal window, run the following command to watch Kubernetes delete and recreate the pod.

kubectl get pod -w -l app=nginx

Expected output:

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

Run the following command to get the name of the recreated pod.

kubectl get pod

Expected output:

NAME                            READY   STATUS      RESTARTS   AGE
nginx-static-78c7dcb9d7-h****   2/2     Running     0          14s

Run the following command to list the files in the /data path. The static file you created still exists, which confirms that the data on the statically provisioned cloud disk is persistent.
```
kubectl exec nginx-static-78c7dcb9d7-h**** -- ls /data
```
Expected output:
```
static
lost+found
```