Using an EVS Disk Through a Dynamic PV

Prerequisites

• You have created a cluster and installed the CCE Container Storage (Everest) add-on in the cluster.
• To create a cluster using commands, ensure kubectl is used. For details, see Connecting to a Cluster Using kubectl.

Constraints

• EVS disks cannot be attached across AZs and cannot be used by multiple workloads, multiple pods of the same workload, or multiple tasks. Data sharing of a shared disk is not supported between nodes in a CCE cluster. If an EVS disk is attacked to multiple nodes, I/O conflicts and data cache conflicts may occur. Therefore, create only one pod when creating a Deployment that uses EVS disks.
• For clusters earlier than v1.19.10, if an HPA policy is used to scale out a workload with EVS volumes mounted, the existing pods cannot be read or written when a new pod is scheduled to another node.

  For clusters of v1.19.10 and later, if an HPA policy is used to scale out a workload with EVS volumes mounted, a new pod cannot be started because EVS disks cannot be attached.

(Console) Automatically Creating an EVS Disk

1. Log in to the CCE console and click the cluster name to access the cluster console.
2. Dynamically create a PVC and PV.
   1. Choose Storage in the navigation pane and click the PVCs tab. Click Create PVC in the upper right corner. In the dialog box displayed, configure the PVC parameters.

      Parameter	Description
      PVC Type	In this example, select EVS.
      PVC Name	Enter the PVC name, which must be unique in the same namespace.
      Creation Method	If no underlying storage is available, select Dynamically provision to create a PVC, PV, and underlying storage on the console in cascading mode. If underlying storage is available, create a storage volume or use an existing storage volume to statically create a PVC based on whether a PV is available. For details, see Using an Existing EVS Disk Through a Static PV. In this example, select Dynamically provision.
      Storage Classes	The storage class for EVS disks is csi-disk.
      AZ	Select the AZ of the EVS disk. The AZ must be the same as that of the cluster node. NOTE: An EVS disk can only be mounted to a node in the same AZ. After an EVS disk is created, its AZ cannot be changed.
      Disk Type	Select an EVS disk type. EVS disk types vary depending on regions. Obtain the available EVS types on the console.
      Access Mode	EVS disks support only ReadWriteOnce, indicating that a storage volume can be mounted to one node in read/write mode. For details, see Volume Access Modes.
      Capacity (GiB)	Capacity of the requested storage volume.
      Enterprise Project	Supported enterprise projects: default, the one to which the cluster belongs, or the one specified by the storage class.

   2. Click Create.

      You can choose Storage in the navigation pane and view the created PVC and PV on the PVCs and PVs tab pages, respectively.

3. Create an application.
   1. In the navigation pane on the left, click Workloads. In the right pane, click the StatefulSets tab.
   2. Click Create Workload in the upper right corner. On the displayed page, click Data Storage in the Container Settings area and click Add Volume to select PVC.
      Mount and use storage volumes, as shown in Table 1. For details about other parameters, see Workloads.

      Table 1 Mounting a storage volume

      Parameter	Description
      PVC	Select an existing EVS volume. An EVS volume cannot be repeatedly mounted to multiple workloads.
      Mount Path	Enter a mount path, for example, /tmp. This parameter indicates the container path to which a data volume will be mounted. Do not mount the volume to a system directory such as / or /var/run. Otherwise, containers will be malfunctional. Mount the volume to an empty directory. If the directory is not empty, ensure that there are no files that affect container startup. Otherwise, the files will be replaced, causing container startup failures or workload creation failures. NOTICE: If a volume is mounted to a high-risk directory, use an account with minimum permissions to start the container. Otherwise, high-risk files on the host machine may be damaged.
      Subpath	Enter the subpath of the storage volume and mount a path in the storage volume to the container. In this way, different folders of the same storage volume can be used in a single pod. tmp, for example, indicates that data in the mount path of the container is stored in the tmp folder of the storage volume. If this parameter is left blank, the root path is used by default.
      Permission	Read-only: You can only read the data in the mounted volumes. Read/Write: You can modify the data volumes mounted to the path. Newly written data will not be migrated if the container is migrated, which may cause data loss.

      In this example, the disk is mounted to the /data path of the container. The container data generated in this path is stored in the EVS disk.

      

      A non-shared EVS disk cannot be attached to multiple pods in a workload. Otherwise, the pods cannot start properly. Ensure that the number of workload pods is 1 when you attach an EVS disk.

      

   3. After the configuration, click Create Workload.

      After the workload is created, the data in the container mount directory will be persistently stored. Verify the storage by referring to Verifying Data Persistence.

(kubectl) Automatically Creating an EVS Disk

1. Use kubectl to access the cluster.
2. Use StorageClass to dynamically create a PVC and PV.
   1. Create the pvc-evs-auto.yaml file.

      apiVersion: v1
      kind: PersistentVolumeClaim
      metadata:
        name: pvc-evs-auto
        namespace: default
        annotations:
            everest.io/disk-volume-type: SAS    # EVS disk type.
      
          everest.io/enterprise-project-id: <your_project_id>  # (Optional) Enterprise project ID. If an enterprise project is specified, use the same enterprise project when creating a PVC. Otherwise, the PVC cannot be bound to a PV.
        labels:
          failure-domain.beta.kubernetes.io/region: <your_region>   # Region of the node where the application is to be deployed.
          failure-domain.beta.kubernetes.io/zone: <your_zone>       # AZ of the node where the application is to be deployed.
      spec:
        accessModes:
        - ReadWriteOnce               # The value must be ReadWriteOnce for EVS disks.
        resources:
          requests:
            storage: 10Gi             # EVS disk capacity, ranging from 1 to 32768.
        storageClassName: csi-disk    # The storage class is EVS.

      Table 2 Key parameters

      Parameter	Mandatory	Description
      failure-domain.beta.kubernetes.io/region	Yes	Region where the cluster is located.
      failure-domain.beta.kubernetes.io/zone	Yes	AZ where the EVS volume is created. It must be the same as the AZ planned for the workload.
      everest.io/disk-volume-type	Yes	EVS disk type. All letters are in uppercase. SAS: high I/O SSD: ultra-high I/O
      everest.io/enterprise-project-id	No	Optional. Enterprise project ID of the EVS disk. If an enterprise project is specified, use the same enterprise project when creating a PVC. Otherwise, the PVC cannot be bound to a PV. To obtain an enterprise project ID, log in to the EPS console, click the name of the target enterprise project, and copy the enterprise project ID.
      storage	Yes	Requested PVC capacity, in Gi. The value ranges from 1 to 32768.
      storageClassName	Yes	The storage class for EVS disks is csi-disk.

   2. Run the following command to create a PVC:

      kubectl apply -f pvc-evs-auto.yaml

3. Create an application.
   1. Create a file named web-evs-auto.yaml. In this example, the EVS volume is mounted to the /data path.

      apiVersion: apps/v1
      kind: StatefulSet
      metadata:
        name: web-evs-auto
        namespace: default
      spec:
        replicas: 1
        selector:
          matchLabels:
            app: web-evs-auto
        serviceName: web-evs-auto   # Headless Service name.
        template:
          metadata:
            labels:
              app: web-evs-auto
          spec:
            containers:
            - name: container-1
              image: nginx:latest
              volumeMounts:
              - name: pvc-disk    # Volume name, which must be the same as the volume name in the volumes field.
                mountPath: /data  # Location where the storage volume is mounted.
            imagePullSecrets:
              - name: default-secret
            volumes:
              - name: pvc-disk    # Volume name, which can be customized.
                persistentVolumeClaim:
                  claimName: pvc-evs-auto    # Name of the created PVC.
      ---
      apiVersion: v1
      kind: Service
      metadata:
        name: web-evs-auto   # Headless Service name.
        namespace: default
        labels:
          app: web-evs-auto
      spec:
        selector:
          app: web-evs-auto
        clusterIP: None
        ports:
          - name: web-evs-auto
            targetPort: 80
            nodePort: 0
            port: 80
            protocol: TCP
        type: ClusterIP

   2. Run the following command to create a workload to which the EVS volume is mounted:

      kubectl apply -f web-evs-auto.yaml

      After the workload is created, the data in the container mount directory will be persistently stored. Verify the storage by referring to Verifying Data Persistence.

Verifying Data Persistence

1. View the deployed application and EVS volume files.
   1. Run the following command to view the created pod:

      kubectl get pod | grep web-evs-auto

      Expected output:

      web-evs-auto-0                  1/1     Running   0               38s

   2. Run the following command to check whether the EVS volume has been mounted to the /data path:

      kubectl exec web-evs-auto-0 -- df | grep data

      Expected output:

      /dev/sdc              10255636     36888  10202364   0% /data

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

      kubectl exec web-evs-auto-0 -- ls /data

      Expected output:

      lost+found

2. Run the following command to create a file named static in the /data path:

   kubectl exec web-evs-auto-0 --  touch /data/static

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

   kubectl exec web-evs-auto-0 -- ls /data

   Expected output:

   lost+found
   static

4. Run the following command to delete the pod named web-evs-auto-0:

   kubectl delete pod web-evs-auto-0

   Expected output:

   pod "web-evs-auto-0" deleted

5. After the deletion, the StatefulSet controller automatically creates a replica with the same name. Run the following command to check whether the files in the /data path have been modified:

   kubectl exec web-evs-auto-0 -- ls /data

   Expected output:

   lost+found
   static

   If the static file still exists, the data in the EVS volume can be stored persistently.

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