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.

Notes and 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 attached to multiple nodes, I/O conflicts and data cache conflicts may occur. Therefore, select 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. In the right pane, click the PVCs tab. Click Create PVC in the upper right corner. In the dialog box displayed, configure PVC parameters.

      Parameter	Description
      PVC Type	In this example, select EVS.
      PVC Name	Enter the PVC name, which must be unique in a 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 PV or use an existing PV to statically create a PVC. For details, see Using an Existing EVS Disk Through a Static PV. In this example, select Dynamically provision.
      Storage Classes	The default StorageClasses for EVS disks are csi-disk and csi-disk-topology. NOTE: If you use the csi-disk (EVS) StorageClass, a PVC and PV will be created immediately. The EVS disk is created with the PV, and then the PVC is bound to the PV. If you use the csi-disk-topology (EVS created with a delay) StorageClass, a PV will not be immediately created when a PVC is created. Instead, the pods that will be associated with the PVC are scheduled first, and then the EVS disk and PV are created, and finally the PV is bound to the PVC.
      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.
      Capacity (GiB)	Capacity of the requested storage volume.
      Access Mode	EVS volumes support only ReadWriteOnce, indicating that a storage volume can be mounted to one node in read/write mode. For details, see Volume Access Modes.
      Enterprise Project	The default enterprise project, the enterprise project to which the cluster belongs, or the enterprise project specified by StorageClass is available.

   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. Choose Workloads in the navigation pane. 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 can be mounted to only one workload.
      Mount Path	Enter a mount path, for example, /tmp. This parameter specifies a container path to which a data volume will be mounted. Do not mount the volume to a system directory such as / or /var/run. This may lead to container errors. 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, leading to 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 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 will be 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 can be attached to only one workload pod. If there are multiple pods, extra pods cannot start properly. Ensure that the number of workload pods is 1 if an EVS disk is attached.

      

   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.

Automatically Creating an EVS Volume Through kubectl

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    # StorageClass 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 StorageClass 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 check 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 check 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

   The static file is retained, indicating that the data in the EVS volume can be stored persistently.

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