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 existing 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 create 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.
  • EVS disks that have been partitioned are not supported.
  • Only ext4 EVS disks are supported.
• Before creating a cluster using commands, ensure kubectl is used to access 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 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 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 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 volume in the cluster. Create a PV in advance. For details, 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 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 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) Using an Existing EVS Disk

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 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 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>   # 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
      
      
        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.
      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	Configure the file system type. The value defaults to ext4.
      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. SAS: high I/O SSD: ultra-high I/O
      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 volume are 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 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.
      
      
        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    # The storage class 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	Storage class name, which must be the same as the storage class of the PV in 1. The storage class 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 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