Use static disks to create PVs for stateful services - Best Practices| Alibaba Cloud Documentation Center

Background information

Scenarios:

Create applications that require high disk I/O and do not require shared data, such as MySQL and Redis.
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 Alibaba Cloud disks as statically provisioned volumes.

Limits

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

Create a PV

Create 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.
Run the following command to create a PV:
```
kubectl create -f pv-static.yaml
```
View results
1. Log on to the ACK console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, find the cluster that you want to manage, and click the cluster name or click Details in the Actions column of the cluster. The Cluster Information page appears.
4. In the left-side pane, click Persistent Volumes.
5. Click the Persistent Volumes tab to view the PV that you created.

Create a PVC

Create 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>

Run the following command to create a PVC:
```
kubectl create -f pvc-static.yaml
```
View results
1. Log on to the ACK console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, find the cluster that you want to manage and click Details in the Actions column of the cluster.
4. In the left-side pane, click Persistent Volumes.
5. Click the Persistent Volume Claims tab to view the PVC that you created.

Create a deployment

Create 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

Run the following command to create a deployment:
```
kubectl create -f static.yaml
```
View results
1. Log on to the ACK console.
2. In the left-side navigation pane, click Clusters.
3. On the Clusters page, find the cluster to which you mounted the NAS file system, and click the cluster name or Applications in the Actions column.
4. In the left-side navigation pane on the page that appears, click Workload.
5. Click the Deployments tab. You can view the old-nginx deployment.

Use static disks for persistent storage

Run the following command to query the pod that runs the application:

kubectl get pod | grep static

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

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

/dev/vdf        20511312    45080  20449848   1% /data

Run the following command to view the files in the /data path:

kubectl exec nginx-static-78c7dcb9d7-g**** ls /data

lost+found

Run the following command to create the static file in the /data path:
```
kubectl exec nginx-static-78c7dcb9d7-g**** touch /data/static
```

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

kubectl exec nginx-static-78c7dcb9d7-g**** ls /data

static
lost+found

Run the following command to delete the pod named nginx-static-78c7dcb9d7-g****.

kubectl delete pod nginx-static-78c7dcb9d7-g****

pod "nginx-static-78c7dcb9d7-g****" deleted

Open another kubectl CLI and run the following command to view the process of how the pod is deleted and a new pod is created in Kubernetes:

kubectl get pod -w -l app=nginx

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 view the newly created pod:

kubectl get pod

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

Run the following command to verify that the static file in the /data path is not deleted. This indicates that data in the static disk is persistently stored.
```
kubectl exec nginx-static-78c7dcb9d7-h6brd ls /data
```
```
static
lost+found
```