Using an Existing EVS Disk Through a Static PV

Prerequisites

• You have created a cluster and installed the CSI add-on (everest) in the cluster.
• You have created an EVS disk that meets the following requirements:
  • The existing EVS disk cannot be a system disk, DSS disk, or shared disk.
  • The device type of the EVS disk must be SCSI (the default device 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.
  • If the EVS disk is encrypted, the key must be available.
  • Only the EVS disks in the enterprise project to which the cluster belongs and the default enterprise project are supported.
  • EVS disks that have partitions or use non-ext4 file systems are not supported.
• If you want to create a cluster using commands, use kubectl to connect to the cluster. 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 disks attached, 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 disks attached, 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 from the navigation pane, and click the PersistentVolumeClaims (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 underlying storage is available, create a storage volume or use an existing storage volume to statically create a PVC based on whether a PV has been created. 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 a PV and PVC at the same time on the console.
      PVa	Select an existing PV in the cluster. Create a PV in advance. For details, see "Creating a storage volume" in Related Operations. In this example, you do not need to set this parameter.
      EVSb	Click Select EVS. On the displayed page, select the EVS disk that meets your requirements and click OK.
      PV Nameb	Enter the PV name, which must be unique in the same cluster.
      Access Modeb	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.
      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 PersistentVolumeClaims (PVCs) and PersistentVolumes (PVs) tab pages.

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; this action may cause container errors. You are advised to 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 a subpath, for example, tmp, indicating that data in the mount path of the container will be stored in the tmp folder of the volume. A subpath is used to mount a local volume so that the same data volume is used in a single pod. 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 is not 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) Using an Existing EVS Disk

1. Use kubectl to connect to 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 PV is deleted while the underlying volume is retained.
        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. The value is fixed to ReadWriteOnce for EVS disks.
        capacity:
          storage: 10Gi       # EVS disk capacity, in the unit of Gi. The value ranges from 1 to 32768.
        csi:
          driver: disk.csi.everest.io     # Dependent storage driver for the mounting.
          fsType: ext4
          volumeHandle: <your_volume_id>   # Volume ID of the EVS disk.
          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/crypt-key-id: <your_key_id>    # (Optional) Encryption key ID. Mandatory for an encrypted disk.
            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              # Storage class 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. Currently, only retain-volume-only is supported. This field 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. For details about the value of region, see Regions and Endpoints.
      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. For details about the value of zone, see Regions and Endpoints.
      volumeHandle	Yes	Volume ID of the EVS disk. To obtain the 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. SATA: common I/O SAS: high I/O SSD: ultra-high I/O
      everest.io/crypt-key-id	No	Mandatory when the EVS disk is encrypted. Enter the encryption key ID selected during EVS disk creation. To obtain the encryption key 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, copy the value of KMS Key ID in the Configuration Information area.
      everest.io/enterprise-project-id	No	Optional. Enterprise project ID of the EVS disk. If an enterprise project is specified, specify the same enterprise project when creating a PVC. Otherwise, the PVC cannot be bound to a PV. To obtain the 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, you are advised to select Retain to prevent data from being deleted by mistake. Delete: If everest.io/reclaim-policy is not specified, both the PV and EVS volare deleted when a PVC is deleted. If everest.io/reclaim-policy is set to retain-volume-only, when a PVC is deleted, the PV is deleted but the EVS resources are retained. Retain: When a PVC is deleted, the PV and underlying storage resources are not deleted. Instead, you must manually delete these resources. After that, the PV is in the Released status and cannot be bound to the PVC again.
      storageClassName	Yes	The storage class name 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/crypt-key-id: <your_key_id>    # (Optional) Encryption key ID. Mandatory for an encrypted disk.
          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    # Storage class type for EVS disks.
        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. For details about the value of region, see Regions and Endpoints.
      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. For details about the value of zone, see Regions and Endpoints.
      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	Storage class name, which must be the same as the storage class of the PV in 1. The storage class name of the EVS volumes 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 view 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 view 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

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

Related Operations