Using an Existing EVS Disk Through a Static PV

Prerequisites

• You have created a cluster and installed the CCE Container Storage (Everest) add-on in the cluster.
• You have created an EVS disk that meets the following requirements:
  • The EVS disk cannot be a system disk, DSS disk, or shared disk.
  • The EVS disk must be of the SCSI type (the default disk type is VBD when you purchase an EVS disk).
  • The EVS disk must be available and not used by other resources.
  • The AZ of the EVS disk must be the same as that of the cluster node. Otherwise, the EVS disk cannot be mounted and the pod cannot start.
  • The EVS disk must be in the default enterprise project or the enterprise project to which the cluster belongs.
  • EVS disks that have been partitioned are not supported.
  • Only ext4 EVS disks are supported.
• 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.

Using an Existing EVS Disk on the Console

1. Log in to the CCE console and click the cluster name to access the cluster console.
2. Statically 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 underlying storage is available, create a PV or use an existing PV to statically create a PVC. If no underlying storage is available, select Dynamically provision. For details, see Using an EVS Disk Through a Dynamic PV. In this example, select Create new to create both a PV and PVC on the console.
      PVa	Select an existing PV in the cluster. For details about how to create a PV, see "Creating a storage volume" in Related Operations. You do not need to specify this parameter in this example.
      EVSb	Click Select EVS. On the displayed page, select the EVS volume that meets your requirements and click OK.
      PV Nameb	Enter the PV name, which must be unique in the same cluster.
      Access Modeb	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.
      Reclaim Policyb	You can select Delete or Retain to specify the reclaim policy of the underlying storage when the PVC is deleted. For details, see PV Reclaim Policy.

      

      a: The parameter is available when Creation Method is set to Use existing.

      b: The parameter is available when Creation Method is set to Create new.

   2. Click Create to create a PVC and a PV.

      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.

Using an Existing EVS Disk Through kubectl

1. Use kubectl to access the cluster.
2. Create a PV. If a PV has been created in your cluster, skip this step.
   1. Create the pv-evs.yaml file.

      apiVersion: v1
      kind: PersistentVolume
      metadata:
        annotations:
          pv.kubernetes.io/provisioned-by: everest-csi-provisioner
          everest.io/reclaim-policy: retain-volume-only         # (Optional) The underlying volume is retained when the PV is deleted.
        name: pv-evs    # PV name
        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     # Access mode, which must be ReadWriteOnce for EVS disks
        capacity:
          storage: 10Gi       # EVS disk capacity, in the unit of GiB. The value ranges from 1 to 32768.
        csi:
          driver: disk.csi.everest.io     # Dependent storage driver for the mounting
          fsType: ext4    # Must be the same as that of the original file system of the disk.
          volumeHandle: <your_volume_id>   # EVS volume ID
          volumeAttributes:
            everest.io/disk-mode: SCSI           # Device type of the EVS disk. Only SCSI is supported.
            everest.io/disk-volume-type: SAS     # EVS disk type
            storage.kubernetes.io/csiProvisionerIdentity: everest-csi-provisioner
      
            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.
        persistentVolumeReclaimPolicy: Delete    # Reclaim policy
        storageClassName: csi-disk              # StorageClass name. The value must be csi-disk for EVS disks.

      Table 2 Key parameters

      Parameter	Mandatory	Description
      everest.io/reclaim-policy: retain-volume-only	No	Optional. Only retain-volume-only is supported. This parameter is valid only when the Everest version is 1.2.9 or later and the reclaim policy is Delete. If the reclaim policy is Delete and the current value is retain-volume-only, the associated PV is deleted while the underlying storage volume is retained, when a PVC is deleted.
      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.
      fsType	Yes	File system type, which defaults to ext4.
      volumeHandle	Yes	Volume ID of the EVS disk. To obtain a volume ID, log in to the Cloud Server Console. In the navigation pane, choose Elastic Volume Service > Disks. Click the name of the target EVS disk to go to its details page. On the Summary tab page, click the copy button after ID.
      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 Cloud Server Console. In the navigation pane, choose Elastic Volume Service > Disks. Click the name of the target EVS disk to go to its details page. On the Summary tab page, click the enterprise project in Management Information to access the enterprise project console. Copy the corresponding ID to obtain the ID of the enterprise project to which the EVS disk belongs.
      persistentVolumeReclaimPolicy	Yes	A reclaim policy is supported when the cluster version is or later than 1.19.10 and the Everest version is or later than 1.2.9. The Delete and Retain reclaim policies are supported. For details, see PV Reclaim Policy. If high data security is required, select Retain to prevent data from being deleted by mistake. Delete: If everest.io/reclaim-policy is not specified, both the PV and EVS disk will be deleted when a PVC is deleted. If everest.io/reclaim-policy is set to retain-volume-only, when a PVC is deleted, the PV will be deleted but the EVS disk will be retained. Retain: When a PVC is deleted, both the PV and underlying storage resources will be retained. You need to manually delete these resources. After the PVC is deleted, the PV is in the Released state and cannot be bound to a PVC again.
      storageClassName	Yes	The StorageClass for EVS disks is csi-disk.

   2. Run the following command to create a PV:

      kubectl apply -f pv-evs.yaml

3. Create a PVC.
   1. Create the pvc-evs.yaml file.

      apiVersion: v1
      kind: PersistentVolumeClaim
      metadata:
        name: pvc-evs
        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. The value must be the same as the storage size of the existing PV.
        storageClassName: csi-disk    # StorageClass is EVS.
        volumeName: pv-evs            # PV name

      Table 3 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.
      storage	Yes	Requested capacity in the PVC, in Gi. The value must be the same as the storage size of the existing PV.
      volumeName	Yes	PV name, which must be the same as the PV name in 1.
      storageClassName	Yes	StorageClass name, which must be the same as the StorageClass of the PV in 1. The StorageClass for EVS disks is csi-disk.

   2. Run the following command to create a PVC:

      kubectl apply -f pvc-evs.yaml

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

      apiVersion: apps/v1
      kind: StatefulSet
      metadata:
        name: web-evs
        namespace: default
      spec:
       replicas: 1            # The number of workload replicas that use the EVS volume must be 1.
        selector:
          matchLabels:
            app: web-evs
        serviceName: web-evs   # Headless Service name
        template:
          metadata:
            labels:
              app: web-evs
          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    # Name of the created PVC
      ---
      apiVersion: v1
      kind: Service
      metadata:
        name: web-evs   # Headless Service name
        namespace: default
        labels:
          app: web-evs
      spec:
        selector:
          app: web-evs
        clusterIP: None
        ports:
          - name: web-evs
            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.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

      Expected output:

      web-evs-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-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-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-0 --  touch /data/static

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

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

   Expected output:

   lost+found
   static

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

   kubectl delete pod web-evs-0

   Expected output:

   pod "web-evs-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-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.

Related Operations