# StorageClass

StorageClass describes the storage class used in the cluster. You need to specify StorageClass when creating a PVC or PV. As of now, CCE provides storage classes such as csi-disk, csi-nas, and csi-obs by default. When defining a PVC, you can use a StorageClassName to automatically create a PV of the corresponding type and automatically create underlying storage resources.

You can run the following command to query the storage classes that CCE supports. You can use the CSI plug-in provided by CCE to customize a storage class, which functions similarly as the default storage classes in CCE.

    # kubectl get sc
    NAME                PROVISIONER                     AGE
    csi-disk            everest-csi-provisioner         17d          # Storage class for EVS disks
    csi-nas             everest-csi-provisioner         17d          # Storage class for SFS file systems
    csi-obs             everest-csi-provisioner         17d          # Storage class for OBS buckets

After a StorageClass is set, PVs can be automatically created and maintained. You only need to specify the StorageClass when creating a PVC, which greatly reduces the workload.

In addition to the predefined storage classes provided by CCE, you can also customize storage classes. The following sections describe the application status, solutions, and methods of customizing storage classes.

#### Challenges

When using storage resources in CCE, the most common method is to specify storageClassName to define the type of storage resources to be created when creating a PVC. The following configuration shows how to use a PVC to apply for an SAS (high I/O) EVS disk (block storage).

    apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      name: pvc-evs-example
      namespace: default
      annotations:
        everest.io/disk-volume-type: SAS
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 10Gi
      storageClassName: csi-disk

If you need to specify the EVS disk type, you can set the everest.io/disk-volume-type field. The value SAS is used as an example here, indicating the high I/O EVS disk type. Or you can choose SATA (common I/O) and SSD (ultra-high I/O).

This configuration method may not work if you want to:

- Set storageClassName only, which is simpler than specifying the EVS disk type by using everest.io/disk-volume-type.
- Avoid modifying YAML files or Helm charts. Some users switch from self-built or other Kubernetes services to CCE and have written YAML files of many applications. In these YAML files, different types of storage resources are specified by different StorageClassNames. When using CCE, they need to modify a large number of YAML files or Helm charts to use storage resources, which is labor-consuming and error-prone.
- Set the default storageClassName for all applications to use the default storage class. In this way, you can create storage resources of the default type without needing to specify storageClassName in the YAML file.

#### Solution

This section describes how to set a custom storage class in CCE and how to set the default storage class. You can specify different types of storage resources by setting storageClassName.

- For the first scenario, you can define custom storageClassNames for SAS and SSD EVS disks. For example, define a storage class named csi-disk-sas for creating SAS disks. The following figure shows the differences before and after you use a custom storage class.

- For the second scenario, you can define a storage class with the same name as that in the existing YAML file without needing to modify storageClassName in the YAML file.
- For the third scenario, you can set the default storage class as described below to create storage resources without specifying storageClassName in YAML files.

      apiVersion: v1
      kind: PersistentVolumeClaim
      metadata:
        name: pvc-evs-example
        namespace: default
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 10Gi

#### Custom Storage Classes

You can customize a high I/O storage class in a YAML file. For example, the name csi-disk-sas indicates that the disk type is SAS (high I/O).

    apiVersion: storage.k8s.io/v1
    kind: StorageClass
    metadata:
      name: csi-disk-sas                          # Name of the high I/O storage class, which can be customized.
    parameters:
      csi.storage.k8s.io/csi-driver-name: disk.csi.everest.io
      csi.storage.k8s.io/fstype: ext4
      everest.io/disk-volume-type: SAS            # High I/O EVS disk type, which cannot be customized.
      everest.io/passthrough: "true"
    provisioner: everest-csi-provisioner
    reclaimPolicy: Delete
    volumeBindingMode: Immediate
    allowVolumeExpansion: true                    # true indicates that capacity expansion is allowed.

For an ultra-high I/O storage class, you can set the class name to csi-disk-ssd to create SSD EVS disk (ultra-high I/O).

    apiVersion: storage.k8s.io/v1
    kind: StorageClass
    metadata:
      name: csi-disk-ssd                       # Name of the ultra-high I/O storage class, which can be customized.
    parameters:
      csi.storage.k8s.io/csi-driver-name: disk.csi.everest.io
      csi.storage.k8s.io/fstype: ext4
      everest.io/disk-volume-type: SSD         # Ultra-high I/O EVS disk type, which cannot be customized.
      everest.io/passthrough: "true"
    provisioner: everest-csi-provisioner
    reclaimPolicy: Delete
    volumeBindingMode: Immediate
    allowVolumeExpansion: true

reclaimPolicy: indicates the recycling policies of the underlying cloud storage. The value can be Delete or Retain.

- Delete: When a PVC is deleted, both the PV and the EVS disk are deleted.
- 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 resource is in the Released state and cannot be bound to the PVC again.

If high data security is required, you are advised to select Retain to prevent data from being deleted by mistake.

After the definition is complete, run the kubectl create commands to create storage resources.

    # kubectl create -f sas.yaml
    storageclass.storage.k8s.io/csi-disk-sas created
    # kubectl create -f ssd.yaml
    storageclass.storage.k8s.io/csi-disk-ssd created

Query the storage class again. Two more types of storage classes are displayed in the command output, as shown below.

    # kubectl get sc
    NAME                PROVISIONER                     AGE
    csi-disk            everest-csi-provisioner         17d
    csi-disk-sas        everest-csi-provisioner         2m28s
    csi-disk-ssd        everest-csi-provisioner         16s
    csi-disk-topology   everest-csi-provisioner         17d
    csi-nas             everest-csi-provisioner         17d
    csi-obs             everest-csi-provisioner         17d
    csi-sfsturbo        everest-csi-provisioner         17d

Other types of storage resources can be defined in the similar way. You can use kubectl to obtain the YAML file and modify it as required.

- File storage

      # kubectl get sc csi-nas -oyaml
      kind: StorageClass
      apiVersion: storage.k8s.io/v1
      metadata:
        name: csi-nas
      provisioner: everest-csi-provisioner
      parameters:
        csi.storage.k8s.io/csi-driver-name: nas.csi.everest.io
        csi.storage.k8s.io/fstype: nfs
        everest.io/share-access-level: rw
        everest.io/share-access-to: 5e3864c6-e78d-4d00-b6fd-de09d432c632   # ID of the VPC to which the cluster belongs
        everest.io/share-is-public: 'false'
        everest.io/zone: xxxxx          # AZ
      reclaimPolicy: Delete
      allowVolumeExpansion: true
      volumeBindingMode: Immediate

- Object storage

      # kubectl get sc csi-obs -oyaml
      kind: StorageClass
      apiVersion: storage.k8s.io/v1
      metadata:
        name: csi-obs
      provisioner: everest-csi-provisioner
      parameters:
        csi.storage.k8s.io/csi-driver-name: obs.csi.everest.io
        csi.storage.k8s.io/fstype: s3fs           # Object storage type. s3fs indicates an object bucket, and obsfs indicates a parallel file system.
        everest.io/obs-volume-type: STANDARD      # Storage class of the OBS bucket
      reclaimPolicy: Delete
      volumeBindingMode: Immediate

#### Setting a Default Storage Class

You can specify a storage class as the default class. In this way, if you do not specify storageClassName when creating a PVC, the PVC is created using the default storage class.

For example, to specify csi-disk-ssd as the default storage class, edit your YAML file as follows:

    apiVersion: storage.k8s.io/v1
    kind: StorageClass
    metadata:
      name: csi-disk-ssd
      annotations:
        storageclass.kubernetes.io/is-default-class: "true"   # Specifies the default storage class in a cluster. A cluster can have only one default storage class.
    parameters:
      csi.storage.k8s.io/csi-driver-name: disk.csi.everest.io
      csi.storage.k8s.io/fstype: ext4
      everest.io/disk-volume-type: SSD
      everest.io/passthrough: "true"
    provisioner: everest-csi-provisioner
    reclaimPolicy: Delete
    volumeBindingMode: Immediate
    allowVolumeExpansion: true

Delete the created csi-disk-ssd disk, run the kubectl create command to create a csi-disk-ssd disk again, and then query the storage class. The following information is displayed.

    # kubectl delete sc csi-disk-ssd
    storageclass.storage.k8s.io "csi-disk-ssd" deleted
    # kubectl create -f ssd.yaml
    storageclass.storage.k8s.io/csi-disk-ssd created
    # kubectl get sc
    NAME                     PROVISIONER                     AGE
    csi-disk                 everest-csi-provisioner         17d
    csi-disk-sas             everest-csi-provisioner         114m
    csi-disk-ssd (default)   everest-csi-provisioner         9s
    csi-disk-topology        everest-csi-provisioner         17d
    csi-nas                  everest-csi-provisioner         17d
    csi-obs                  everest-csi-provisioner         17d
    csi-sfsturbo             everest-csi-provisioner         17d

#### Verification

- Use csi-disk-sas to create a PVC.

      apiVersion: v1
      kind: PersistentVolumeClaim
      metadata:
        name:  sas-disk
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 10Gi
        storageClassName: csi-disk-sas

  Create a storage class and view its details. As shown below, the object can be created and the value of STORAGECLASS is csi-disk-sas.

      # kubectl create -f sas-disk.yaml
      persistentvolumeclaim/sas-disk created
      # kubectl get pvc
      NAME       STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
      sas-disk   Bound    pvc-6e2f37f9-7346-4419-82f7-b42e79f7964c   10Gi       RWO            csi-disk-sas   24s
      # kubectl get pv
      NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM                     STORAGECLASS   REASON   AGE
      pvc-6e2f37f9-7346-4419-82f7-b42e79f7964c   10Gi       RWO            Delete           Bound       default/sas-disk          csi-disk-sas            30s

  View the PVC details on the CCE console. On the PV details page, you can see that the disk type is high I/O.

- If storageClassName is not specified, the default configuration is used, as shown below.

      apiVersion: v1
      kind: PersistentVolumeClaim
      metadata:
        name:  ssd-disk
      spec:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 10Gi

  Create and view the storage resource. You can see that the storage class of PVC ssd-disk is csi-disk-ssd, indicating that csi-disk-ssd is used by default.

      # kubectl create -f ssd-disk.yaml
      persistentvolumeclaim/ssd-disk created
      # kubectl get pvc
      NAME       STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
      sas-disk   Bound    pvc-6e2f37f9-7346-4419-82f7-b42e79f7964c   10Gi       RWO            csi-disk-sas   16m
      ssd-disk   Bound    pvc-4d2b059c-0d6c-44af-9994-f74d01c78731   10Gi       RWO            csi-disk-ssd   10s
      # kubectl get pv
      NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM                     STORAGECLASS   REASON   AGE
      pvc-4d2b059c-0d6c-44af-9994-f74d01c78731   10Gi       RWO            Delete           Bound       default/ssd-disk          csi-disk-ssd            15s
      pvc-6e2f37f9-7346-4419-82f7-b42e79f7964c   10Gi       RWO            Delete           Bound       default/sas-disk          csi-disk-sas            17m

  View the PVC details on the CCE console. On the PV details page, you can see that the disk type is ultra-high I/O.

Parent topic: Storage (CSI)