# How Do I Change the Storage Class Used by a Cluster of v1.15 from FlexVolume to CSI Everest?

For clusters of v1.15.11-r1 and later, the CSI everest add-on has taken over all functions of the fuxi FlexVolume driver (the storage-driver add-on) for container storage management. In versions later than 1.17.9-r0, the fuxi FlexVolume driver (storage-driver) is no longer supported.

To migrate your storage volumes, create a static PV to associate with the original underlying storage, and then create a PVC to associate with this static PV. When you upgrade your application, mount the new PVC to the original mounting path to migrate the storage volumes.

Services will be interrupted during the migration. Therefore, properly plan the migration and back up data.

#### Procedure

1. (Optional) Back up data to prevent data loss in case of exceptions.
2. Run kubectl commands.
3. Configure a YAML file of the PV in the CSI format according to the PV in the FlexVolume format and associate the PV with the existing storage.

   To be specific, run the following commands to configure the pv-example.yaml file, which is used to create a PV.

   touch pv-example.yaml

   vi pv-example.yaml

   Configuration example of a PV for an EVS volume:

       apiVersion: v1
       kind: PersistentVolume
       metadata:
         labels:
           failure-domain.beta.kubernetes.io/region: eu-de
           failure-domain.beta.kubernetes.io/zone: eu-de-01
         annotations:
           pv.kubernetes.io/provisioned-by: everest-csi-provisioner
         name: pv-evs-example
       spec:
         accessModes:
         - ReadWriteOnce
         capacity:
           storage: 10Gi
         csi:
           driver: disk.csi.everest.io
           fsType: ext4
           volumeAttributes:
             everest.io/disk-mode: SCSI
             everest.io/disk-volume-type: SATA
             storage.kubernetes.io/csiProvisionerIdentity: everest-csi-provisioner
           volumeHandle: 0992dbda-6340-470e-a74e-4f0db288ed82
         persistentVolumeReclaimPolicy: Delete
         storageClassName: csi-disk

   Pay attention to the fields in bold and red. The parameters are described as follows:

   Table 1 EVS volume configuration parameters
   Parameter | Description
   --- | ---
   failure-domain.beta.kubernetes.io/region | Region where the EVS disk is located. Use the same value as that of the FlexVolume PV.
   failure-domain.beta.kubernetes.io/zone | AZ where the EVS disk is located. Use the same value as that of the FlexVolume PV.
   name | Name of the PV, which must be unique in the cluster.
   storage | EVS volume capacity in the unit of Gi. Use the value of spec.capacity.storage of the FlexVolume PV.
   driver | Storage driver used to attach the volume. Set the driver to disk.csi.everest.io for the EVS volume.
   volumeHandle | Volume ID of the EVS disk. Use the value of spec.flexVolume.options.volumeID of the FlexVolume PV.
   everest.io/disk-mode | EVS disk mode. Use the value of spec.flexVolume.options.disk-mode of the FlexVolume PV.
   everest.io/disk-volume-type | EVS disk type. Currently, high I/O (SAS), ultra-high I/O (SSD), and common I/O (SATA) are supported. Use the value of kubernetes.io/volumetype in the storage class corresponding to spec.storageClassName of the FlexVolume PV.
   storageClassName | Name of the Kubernetes storage class associated with the storage volume. Set this field to csi-disk for EVS disks.

   Configuration example of a PV for an SFS volume:

       apiVersion: v1
       kind: PersistentVolume
       metadata:
         name: pv-sfs-example
         annotations:
           pv.kubernetes.io/provisioned-by: everest-csi-provisioner
       spec:
         accessModes:
         - ReadWriteMany
         capacity:
           storage: 10Gi
         csi:
           driver: nas.csi.everest.io
           fsType: nfs
           volumeAttributes:
             everest.io/share-export-location: sfs-nas01.Endpoint:/share-436304e8
             storage.kubernetes.io/csiProvisionerIdentity: everest-csi-provisioner
           volumeHandle: 682f00bb-ace0-41d8-9b3e-913c9aa6b695
         persistentVolumeReclaimPolicy: Delete
         storageClassName: csi-nas

   Pay attention to the fields in bold and red. The parameters are described as follows:

   Table 2 SFS volume configuration parameters
   Parameter | Description
   --- | ---
   name | Name of the PV, which must be unique in the cluster.
   storage | File storage size in the unit of Gi. Use the value of spec.capacity.storage of the FlexVolume PV.
   driver | Storage driver used to attach the volume. Set the driver to nas.csi.everest.io for the file system.
   everest.io/share-export-location | Shared path of the file system. Use the value of spec.flexVolume.options.deviceMountPath of the FlexVolume PV.
   volumeHandle | File system ID. Use the value of spec.flexVolume.options.volumeID of the FlexVolume PV.
   storageClassName | Name of the Kubernetes storage class. Set this field to csi-nas.

   Configuration example of a PV for an OBS volume:

       apiVersion: v1
       kind: PersistentVolume
       metadata:
         name: pv-obs-example
         annotations:
           pv.kubernetes.io/provisioned-by: everest-csi-provisioner
       spec:
         accessModes:
         - ReadWriteMany
         capacity:
           storage: 1Gi
         csi:
           driver: obs.csi.everest.io
           fsType: s3fs
           volumeAttributes:
             everest.io/obs-volume-type: STANDARD
             everest.io/region: eu-de
             storage.kubernetes.io/csiProvisionerIdentity: everest-csi-provisioner
           volumeHandle: obs-normal-static-pv
         persistentVolumeReclaimPolicy: Delete
         storageClassName: csi-obs

   Pay attention to the fields in bold and red. The parameters are described as follows:

   Table 3 OBS volume configuration parameters
   Parameter | Description
   --- | ---
   name | Name of the PV, which must be unique in the cluster.
   storage | Storage capacity in the unit of Gi. Set this parameter to the fixed value 1Gi.
   driver | Storage driver used to attach the volume. Set the driver to obs.csi.everest.io for the OBS volume.

   fsType

   File type. Value options are obsfs or s3fs. If the value is s3fs, an OBS bucket is created and mounted using s3fs. If the value is obsfs, an OBS parallel file system is created and mounted using obsfs. Set this parameter according to the value of spec.flexVolume.options.posix of the FlexVolume PV. If the value of spec.flexVolume.options.posix is true, set this parameter to obsfs. If the value is false, set this parameter to s3fs.

   everest.io/obs-volume-type | Storage class, including STANDARD (standard bucket) and WARM (infrequent access bucket). Set this parameter according to the value of spec.flexVolume.options.storage_class of the FlexVolume PV. If the value of spec.flexVolume.options.storage_class is standard, set this parameter to STANDARD. If the value is standard_ia, set this parameter to WARM.
   everest.io/region | Region where the OBS bucket is located. Use the value of spec.flexVolume.options.region of the FlexVolume PV.
   volumeHandle | OBS bucket name. Use the value of spec.flexVolume.options.volumeID of the FlexVolume PV.
   storageClassName | Name of the Kubernetes storage class. Set this field to csi-obs.

   Configuration example of a PV for an SFS Turbo volume:

       apiVersion: v1
       kind: PersistentVolume
       metadata:
         name: pv-efs-example
         annotations:
           pv.kubernetes.io/provisioned-by: everest-csi-provisioner
       spec:
         accessModes:
         - ReadWriteMany
         capacity:
           storage: 10Gi
         csi:
           driver: sfsturbo.csi.everest.io
           fsType: nfs
           volumeAttributes:
             everest.io/share-export-location: 192.168.0.169:/
             storage.kubernetes.io/csiProvisionerIdentity: everest-csi-provisioner
           volumeHandle: 8962a2a2-a583-4b7f-bb74-fe76712d8414
         persistentVolumeReclaimPolicy: Delete
         storageClassName: csi-sfsturbo

   Pay attention to the fields in bold and red. The parameters are described as follows:

   Table 4 SFS Turbo volume configuration parameters
   Parameter | Description
   --- | ---
   name | Name of the PV, which must be unique in the cluster.
   storage | File system size. Use the value of spec.capacity.storage of the FlexVolume PV.
   driver | Storage driver used to attach the volume. Set it to sfsturbo.csi.everest.io.
   everest.io/share-export-location | Shared path of the SFS Turbo volume. Use the value of spec.flexVolume.options.deviceMountPath of the FlexVolume PV.
   volumeHandle | SFS Turbo volume ID. Use the value of spec.flexVolume.options.volumeID of the FlexVolume PV.
   storageClassName | Name of the Kubernetes storage class. Set this field to csi-sfsturbo for SFS Turbo volumes.

4. Configure a YAML file of the PVC in the CSI format according to the PVC in the FlexVolume format and associate the PVC with the PV created in 3.

   To be specific, run the following commands to configure the pvc-example.yaml file, which is used to create a PVC.

   touch pvc-example.yaml

   vi pvc-example.yaml

   Configuration example of a PVC for an EVS volume:

       apiVersion: v1
       kind: PersistentVolumeClaim
       metadata:
         labels:
           failure-domain.beta.kubernetes.io/region: eu-de
           failure-domain.beta.kubernetes.io/zone: eu-de-01
         annotations:
           everest.io/disk-volume-type: SATA
           volume.beta.kubernetes.io/storage-provisioner: everest-csi-provisioner
         name: pvc-evs-example
         namespace: default
       spec:
         accessModes:
         - ReadWriteOnce
         resources:
           requests:
             storage: 10Gi
         volumeName:  pv-evs-example
         storageClassName: csi-disk

   Pay attention to the fields in bold and red. The parameters are described as follows:

   Table 5 PVC configuration parameters for an EVS volume
   Parameter | Description
   --- | ---
   failure-domain.beta.kubernetes.io/region | Region where the cluster is located. Use the same value as that of the FlexVolume PVC.
   failure-domain.beta.kubernetes.io/zone | AZ where the EVS disk is deployed. Use the same value as that of the FlexVolume PVC.
   everest.io/disk-volume-type | Storage class of the EVS disk. The value can be SAS, SSD, or SATA. Set this parameter to the same value as that of the PV created in 3.
   name | PVC name, which must be unique in the namespace. The value must be unique in the namespace. (If the PVC is dynamically created by a stateful application, the value of this parameter must be the same as the name of the FlexVolume PVC.)
   namespace | Namespace to which the PVC belongs. Use the same value as that of the FlexVolume PVC.
   storage | Requested capacity of the PVC, which must be the same as the storage size of the existing PV.
   volumeName | Name of the PV. Set this parameter to the name of the static PV in 3.
   storageClassName | Name of the Kubernetes storage class. Set this field to csi-disk for EVS disks.

   Configuration example of a PVC for an SFS volume:

       apiVersion: v1
       kind: PersistentVolumeClaim
       metadata:
         annotations:
           volume.beta.kubernetes.io/storage-provisioner: everest-csi-provisioner
         name: pvc-sfs-example
         namespace: default
       spec:
         accessModes:
         - ReadWriteMany
         resources:
           requests:
             storage: 10Gi
         storageClassName: csi-nas
         volumeName: pv-sfs-example

   Pay attention to the fields in bold and red. The parameters are described as follows:

   Table 6 PVC configuration parameters for an SFS volume
   Parameter | Description
   --- | ---
   name | PVC name, which must be unique in the namespace. The value must be unique in the namespace. (If the PVC is dynamically created by a stateful application, the value of this parameter must be the same as the name of the FlexVolume PVC.)
   namespace | Namespace to which the PVC belongs. Use the same value as that of the FlexVolume PVC.
   storage | Storage capacity, in the unit of Gi. The value must be the same as the storage size of the existing PV.
   storageClassName | Set this field to csi-nas.
   volumeName | Name of the PV. Set this parameter to the name of the static PV in 3.

   Configuration example of a PVC for an OBS volume:

       apiVersion: v1
       kind: PersistentVolumeClaim
       metadata:
         annotations:
           volume.beta.kubernetes.io/storage-provisioner: everest-csi-provisioner
           everest.io/obs-volume-type: STANDARD
           csi.storage.k8s.io/fstype: s3fs
         name: pvc-obs-example
         namespace: default
       spec:
         accessModes:
         - ReadWriteMany
         resources:
           requests:
             storage: 1Gi
         storageClassName: csi-obs
         volumeName: pv-obs-example

   Pay attention to the fields in bold and red. The parameters are described as follows:

   Table 7 PVC configuration parameters for an OBS volume
   Parameter | Description
   --- | ---
   everest.io/obs-volume-type | OBS volume type, which can be STANDARD (standard bucket) and WARM (infrequent access bucket). Set this parameter to the same value as that of the PV created in 3.
   csi.storage.k8s.io/fstype | File type, which can be obsfs or s3fs. The value must be the same as that of fsType of the static OBS volume PV.
   name | PVC name, which must be unique in the namespace. The value must be unique in the namespace. (If the PVC is dynamically created by a stateful application, the value of this parameter must be the same as the name of the FlexVolume PVC.)
   namespace | Namespace to which the PVC belongs. Use the same value as that of the FlexVolume PVC.
   storage | Storage capacity in the unit of Gi. Set this parameter to the fixed value 1Gi.
   storageClassName | Name of the Kubernetes storage class. Set this field to csi-obs.
   volumeName | Name of the PV. Set this parameter to the name of the static PV created in 3.

   Configuration example of a PVC for an SFS Turbo volume:

       apiVersion: v1
       kind: PersistentVolumeClaim
       metadata:
         annotations:
           volume.beta.kubernetes.io/storage-provisioner: everest-csi-provisioner
         name: pvc-efs-example
         namespace: default
       spec:
         accessModes:
         - ReadWriteMany
         resources:
           requests:
             storage: 10Gi
         storageClassName: csi-sfsturbo
         volumeName: pv-efs-example

   Pay attention to the fields in bold and red. The parameters are described as follows:

   Table 8 PVC configuration parameters for an SFS Turbo volume
   Parameter | Description
   --- | ---
   name | PVC name, which must be unique in the namespace. The value must be unique in the namespace. (If the PVC is dynamically created by a stateful application, the value of this parameter must be the same as the name of the FlexVolume PVC.)
   namespace | Namespace to which the PVC belongs. Use the same value as that of the FlexVolume PVC.
   storageClassName | Name of the Kubernetes storage class. Set this field to csi-sfsturbo.
   storage | Storage capacity, in the unit of Gi. The value must be the same as the storage size of the existing PV.
   volumeName | Name of the PV. Set this parameter to the name of the static PV created in 3.

5. Upgrade the workload to use a new PVC.

   For Deployments
   1. Run the kubectl create -f commands to create a PV and PVC.

      kubectl create -f pv-example.yaml

      kubectl create -f pvc-example.yaml

      Replace the example file name pvc-example.yaml in the preceding commands with the names of the YAML files configured in 3 and 4.

   2. Go to the CCE console. On the workload upgrade page, click Upgrade > Advanced Settings > Data Storage > Cloud Storage.
   3. Uninstall the old storage and add the PVC in the CSI format. Retain the original mounting path in the container.
   4. Click Submit.
   5. Wait until the pods are running.

   For StatefulSets that use existing storage

   1. Run the kubectl create -f commands to create a PV and PVC.

      kubectl create -f pv-example.yaml

      kubectl create -f pvc-example.yaml

      Replace the example file name pvc-example.yaml in the preceding commands with the names of the YAML files configured in 3 and 4.

   2. Run the kubectl edit command to edit the StatefulSet and use the newly created PVC.

      kubectl edit sts sts-example -n xxx

      Replace sts-example in the preceding command with the actual name of the StatefulSet to upgrade. xxx indicates the namespace to which the StatefulSet belongs.

   3. Wait until the pods are running.

   The current console does not support the operation of adding new cloud storage for StatefulSets. Use the kubectl commands to replace the storage with the newly created PVC.

   For StatefulSets that use dynamically allocated storage

   1. Back up the PV and PVC in the flexVolume format used by the StatefulSet.

      kubectl get pvc xxx -n {namespaces} -oyaml > pvc-backup.yaml

      kubectl get pv xxx -n {namespaces} -oyaml > pv-backup.yaml

   2. Change the number of pods to 0.
   3. On the storage page, disassociate the flexVolume PVC used by the StatefulSet.
   4. Run the kubectl create -f commands to create a PV and PVC.

      kubectl create -f pv-example.yaml

      kubectl create -f pvc-example.yaml

      Replace the example file name pvc-example.yaml in the preceding commands with the names of the YAML files configured in 3 and 4.

   5. Change the number of pods back to the original value and wait until the pods are running.

   The dynamic allocation of storage for StatefulSets is achieved by using volumeClaimTemplates. This field cannot be modified by Kubernetes. Therefore, data cannot be migrated by using a new PVC.

   The PVC naming rule of the volumeClaimTemplates is fixed. When a PVC that meets the naming rule exists, this PVC is used.

   Therefore, disassociate the original PVC first, and then create a PVC with the same name in the CSI format.

   6. (Optional) Recreate the stateful application to ensure that a CSI PVC is used when the application is scaled out. Otherwise, FlexVolume PVCs are used in scaling out.

   - Run the following command to obtain the YAML file of the StatefulSet:

   kubectl get sts xxx -n {namespaces} -oyaml > sts.yaml

   - Run the following command to back up the YAML file of the StatefulSet:

   cp sts.yaml sts-backup.yaml

   - Modify the definition of volumeClaimTemplates in the YAML file of the StatefulSet.

   vi sts.yaml

   Configuration example of volumeClaimTemplates for an EVS volume:

         volumeClaimTemplates:
           - metadata:
               name: pvc-161070049798261342
               namespace: default
               creationTimestamp: null
               annotations:
                 everest.io/disk-volume-type: SATA
             spec:
               accessModes:
                 - ReadWriteOnce
               resources:
                 requests:
                   storage: 10Gi
               storageClassName: csi-disk

   The parameter value must be the same as the PVC of the EVS volume created in 4.

   Configuration example of volumeClaimTemplates for an SFS volume:

         volumeClaimTemplates:
           - metadata:
               name: pvc-161063441560279697
               namespace: default
               creationTimestamp: null
             spec:
               accessModes:
                 - ReadWriteMany
               resources:
                 requests:
                   storage: 10Gi
               storageClassName: csi-na

   The parameter value must be the same as the PVC of the SFS volume created in 4.

   Configuration example of volumeClaimTemplates for an OBS volume:

         volumeClaimTemplates:
           - metadata:
               name: pvc-161070100417416148
               namespace: default
               creationTimestamp: null
               annotations:
                 csi.storage.k8s.io/fstype: s3fs
                 everest.io/obs-volume-type: STANDARD
             spec:
               accessModes:
                 - ReadWriteMany
               resources:
                 requests:
                   storage: 1Gi
               storageClassName: csi-obs

   The parameter value must be the same as the PVC of the OBS volume created in 4.

   - Delete the StatefulSet.

   kubectl delete sts xxx -n {namespaces}

   - Create the StatefulSet.

   kubectl create -f sts.yaml

6. Check service functions.

   1. Check whether the application is running properly.
   2. Checking whether the data storage is normal.

   If a rollback is required, perform 5. Select the PVC in FlexVolume format and upgrade the application.

7. Uninstall the PVC in the FlexVolume format.

   If the application functions normally, unbind the PVC in the FlexVolume format on the storage management page.

   You can also run the kubectl command to delete the PVC and PV of the FlexVolume format.

   Before deleting a PV, change the persistentVolumeReclaimPolicy policy of the PV to Retain. Otherwise, the underlying storage will be reclaimed after the PV is deleted.

Parent topic: Reference