How to mount a disk to an ECI Pod using a PVC - Elastic Container Instance

Prerequisites

A VNode is deployed in your self-managed Kubernetes cluster.
Your cluster runs Kubernetes 1.16 or later and has the CSI-Provisioner component deployed.

Important
For deployment instructions for the CSI-Provisioner component, see alibaba-cloud-csi-driver. If you encounter issues during deployment, submit an issue on GitHub.
If your Kubernetes cluster is deployed in an on-premises data center, ensure a connection exists between the data center and Alibaba Cloud.

Usage notes

Disks are non-shared storage and can be mounted to only one pod at a time.
You can mount a disk only to an ECI pod that runs on a VNode in the same zone. Cross-zone mounting is not supported.

Statically mount a disk

Create a disk.
1. Log on to the ECS console.
2. Create a pay-as-you-go disk in the same region and zone as the VNode.
  
  For more information about how to create a disk, see Create a data disk. After the disk is created, record its ID.
  
  Note
  If you use an existing disk, make sure it is in the same region and zone as the VNode, and that it has not been partitioned or formatted.

Create a PersistentVolume (PV).

Create a file named static-disk-pv.yaml with the following content.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: static-disk-pv
  labels:
    alicloud-pvname: static-disk-pv
spec:
  capacity:
    storage: 25Gi
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  csi:
    driver: diskplugin.csi.alibabacloud.com
    volumeHandle: "<your disk-id>"    # Replace with the ID of your disk.
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: topology.diskplugin.csi.alibabacloud.com/zone
          operator: In
          values:
          - "<your-node-zone-id>"   # Replace with the zone where the VNode resides.

The following table describes the parameters.

Parameter	Description
driver	The driver type. Set this parameter to `diskplugin.csi.alibabacloud.com` to use the Alibaba Cloud disk CSI plugin.
volumeHandle	The disk ID.

Run the following command to create the PV.
```
kubectl create -f static-disk-pv.yaml
```

Create a PersistentVolumeClaim (PVC).

Save the following content as static-disk-pvc.yaml.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: static-disk-pvc
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 25Gi
  selector:
    matchLabels:
      alicloud-pvname: static-disk-pv

Run the following command to create the PVC.
```
kubectl create -f static-disk-pvc.yaml
```

Mount the disk to an ECI pod.

Save the following content as static-disk-test.yaml.

apiVersion: v1
kind: Pod
metadata:
  name: static-disk-test
  labels:
    alibabacloud.com/eci: "true"
spec:
  nodeSelector:
    k8s.aliyun.com/vnode: "true"
  tolerations:
  - key: k8s.aliyun.com/vnode
    operator: "Equal"
    value: "true"
    effect: "NoSchedule"
  containers:
  - name: nginx
    image: registry-vpc.cn-beijing.aliyuncs.com/eci_open/nginx:1.14.2
    ports:
    - containerPort: 80
      name: web
    volumeMounts:
    - name: pvc-disk
      mountPath: /data
  volumes:
    - name: pvc-disk
      persistentVolumeClaim:
        claimName: static-disk-pvc

Run the following command to create the pod.
```
kubectl create -f static-disk-test.yaml
```

Verify the result.

kubectl get pods -o wide

NAME                 READY   STATUS    RESTARTS   AGE   IP            NODE                                  NOMINATED NODE   READINESS GATES
static-disk-test     1/1     Running   0          44s   172.16.XX.XX   cn-beijing.vnd-2ze8nd8xcl33t4pa****   <none>           <none>

Check the directories in the pod. The mount directory /data for the disk is created.

[root@k8s-01 ~]# kubectl exec -it static-disk-test  -- bash
root@static-disk-test:/# ls
bin  boot  data  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var
root@static-disk-test:/# ls /data
lost+found

Dynamically mount a disk

Create a StorageClass.

Create a file named disk-sc.yaml with the following content.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: alicloud-disk-essd
provisioner: diskplugin.csi.alibabacloud.com
parameters:
  type: cloud_essd
  regionId: cn-beijing 
  zoneId: cn-beijing-l 
  fstype: ext4
  readonly: "true"
  mkfsOptions: "-O project,quota"
  diskTags: "key1:value1,key2:value2"
  encrypted: "false"
  performanceLevel: PL1
volumeBindingMode: Immediate
reclaimPolicy: Delete
allowVolumeExpansion: true

The following table describes the parameters.

Parameter	Description
provisioner	The driver type. Set this parameter to `diskplugin.csi.alibabacloud.com` to use the Alibaba Cloud disk CSI plugin.
type	The disk category. Valid values: `cloud_essd`: ESSD `cloud_ssd`: standard SSD cloud_efficiency: ultra disk. `available`: The system attempts to create a standard SSD first. If standard SSDs are unavailable in the zone, the system creates an ultra disk instead. Note You can also specify a comma-separated list of disk categories other than `available`. For example, `type: cloud_efficiency, cloud_ssd, cloud_essd`. The system then attempts to create a disk from each specified category in order until one is successfully created.
regionId, zoneId	The region and zone of the disk. They must be the same as those of the VNode.
fstype	The file system of the disk. The default value is `ext4`.
readonly	Specifies whether the disk is mounted as read-only. The default value is `false`. `true`: The disk is read-only. `false`: The disk is read-write.
mkfsOptions	The parameters used to format the disk. Example: `mkfsOptions: "-O project,quota"`.
diskTags	The tags to add to the disk. The format is `key1:value1,key2:value2`.
encrypted	Specifies whether to encrypt the disk. The default is `false`.
performanceLevel	The performance level of the ESSD. Valid values: `PL0`, `PL1`, `PL2`, and `PL3`. For more information, see ESSDs.
volumeBindingMode	The binding mode of the disk. The default value is `Immediate`.
reclaimPolicy	The reclaim policy for the disk. The default value is `Delete`. `Retain` is also supported. `Delete`: When the PVC is deleted, the PV and the disk are also deleted. `Retain`: When the PVC is deleted, the PV and the disk are not deleted. You must manually delete them. If data security is a high priority, use the `Retain` policy to prevent accidental data loss.
allowVolumeExpansion	Specifies whether to allow automatic expansion for the disk.

Run the following command to create the StorageClass.
```
kubectl create -f disk-sc.yaml
```

Create a PVC.

Save the following content as disk-pvc.yaml.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: disk-pvc
spec:
  accessModes:
  - ReadWriteOnce
  volumeMode: Filesystem
  resources:
    requests:
      storage: 25Gi
  storageClassName: alicloud-disk-essd

Run the following command to create the PVC.
```
kubectl create -f disk-pvc.yaml
```
The system automatically creates a disk and the corresponding PV based on the StorageClass configuration.

Mount the disk to an ECI pod.

Save the following content as disk-test.yaml.

Note

Use a StatefulSet to mount the disk instead of a Deployment. Deployments are intended for stateless services and do not guarantee that pod state is preserved across restarts. In a multi-replica Deployment, you cannot configure an independent volume for each pod.

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: disk-test
spec:
  selector:
    matchLabels:
      app: nginx
  serviceName: "nginx"
  template:
    metadata:
      labels:
        app: nginx
    spec:
      nodeSelector:    
        k8s.aliyun.com/vnode: "true"
      tolerations:     
      - key: k8s.aliyun.com/vnode
        operator: "Equal"
        value: "true"
        effect: "NoSchedule"
      containers:
      - name: nginx
        image: registry-vpc.cn-beijing.aliyuncs.com/eci_open/nginx:1.14.2
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: pvc-disk
          mountPath: /data
      volumes:
        - name: pvc-disk
          persistentVolumeClaim:
            claimName: disk-pvc

Run the following command to create the StatefulSet.
```
kubectl create -f disk-test.yaml
```

Verify the result.

kubectl get pods -o wide

Expected output:

NAME                              READY   STATUS              RESTARTS   AGE     IP             NODE                                  NOMINATED NODE   READINESS GATES
disk-test-0                       1/1     Running             0          3m58s   172.16.XX.XX   cn-beijing.vnd-2ze8nd8xcl33t4pa****   <none>           <none>

Check the directories in the pod. The mount directory /data for the disk is created.

[root@k8s-master ~]# kubectl exec -it disk-test-0 -- bash
root@disk-test-0:/# ls
bin  boot  data  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr
root@disk-test-0:/# ls /data
lost+found