Help Center/ Cloud Container Engine/ User Guide (Ankara Region)/ Storage/ StorageClass
Updated on 2024-12-04 GMT+08:00
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StorageClass

Introduction

StorageClass describes the classification of storage types in a cluster and can be represented as a configuration template for creating PVs. When creating a PVC or PV, specify StorageClass.

As a user, you only need to specify storageClassName when defining a PVC to automatically create a PV and underlying storage, significantly reducing the workload of creating and maintaining a PV.

In addition to the default storage classes provided by CCE, you can also customize storage classes.

CCE Default Storage Classes

As of now, CCE provides StorageClasses such as csi-disk 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.

Run the following kubectl command to obtain the storage classes that CCE supports. Use the CSI add-on provided by CCE to create a storage class.

# kubectl get sc
NAME                PROVISIONER                     AGE
csi-disk            everest-csi-provisioner         17d          # EVS disk
csi-disk-topology   everest-csi-provisioner         17d          # EVS disks created with delayed

csi-obs             everest-csi-provisioner         17d          # OBS
Each storage class contains the default parameters used for dynamically creating a PV. The following is an example of storage class for EVS disks: 
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: csi-disk
provisioner: everest-csi-provisioner
parameters:
  csi.storage.k8s.io/csi-driver-name: disk.csi.everest.io
csi.storage.k8s.io/fstype: ext4
  everest.io/disk-volume-type: SAS
  everest.io/passthrough: 'true'
reclaimPolicy: Delete
allowVolumeExpansion: true
volumeBindingMode: Immediate
Table 1 Key parameters

Parameter

Description

provisioner

Specifies the storage resource provider, which is the Everest add-on for CCE. Set this parameter to everest-csi-provisioner.

parameters

Specifies the storage parameters, which vary with storage types. For details, see Table 2.

reclaimPolicy

Specifies the value of persistentVolumeReclaimPolicy for creating a PV. The value can be Delete or Retain. If reclaimPolicy is not specified when a StorageClass object is created, the value defaults to Delete.

  • Delete: indicates that a dynamically created PV will be automatically destroyed.
  • Retain: indicates that a dynamically created PV will not be automatically destroyed.

allowVolumeExpansion

Specifies whether the PV of this storage class supports dynamic capacity expansion. The default value is false. Dynamic capacity expansion is implemented by the underlying storage add-on. This is only a switch.

volumeBindingMode

Specifies the volume binding mode, that is, the time when a PV is dynamically created. The value can be Immediate or WaitForFirstConsumer.

  • Immediate: PV binding and dynamic creation are completed when a PVC is created.
  • WaitForFirstConsumer: PV binding and creation are delayed. The PV creation and binding processes are executed only when the PVC is used in the workload.

mountOptions

This field must be supported by the underlying storage. If this field is not supported but is specified, the PV creation will fail.
Table 2 Parameters

Volume Type

Parameter

Mandatory

Description

EVS

csi.storage.k8s.io/csi-driver-name

Yes

Driver type. If an EVS disk is used, the parameter value is fixed at disk.csi.everest.io.

csi.storage.k8s.io/fstype

Yes

If an EVS disk is used, the parameter value can be ext4.

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/passthrough

Yes

The parameter value is fixed at true, which indicates that the EVS device type is SCSI. Other parameter values are not allowed.

OBS

csi.storage.k8s.io/csi-driver-name

Yes

Driver type. If OBS is used, the parameter value is fixed at obs.csi.everest.io.

csi.storage.k8s.io/fstype

Yes

Instance type, which can be obsfs or s3fs.

  • obsfs: Parallel file system, which is mounted using obsfs (recommended).
  • s3fs: Object bucket, which is mounted using s3fs.

everest.io/obs-volume-type

Yes

OBS storage class.

  • If fsType is set to s3fs, STANDARD (standard bucket) and WARM (infrequent access bucket) are supported.
  • This parameter is invalid when fsType is set to obsfs.

Application Scenarios of Custom Storage

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 a 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

To specify the EVS disk type on CCE, use the everest.io/disk-volume-type field. SAS indicates the EVS disk type.

The preceding is a basic method of using StorageClass. In real-world scenarios, you can use StorageClass to perform other operations.

Application Scenario

Solution

Procedure

When annotations is used to specify storage configuration, the configuration is complex. For example, the everest.io/disk-volume-type field is used to specify the EVS disk type.

Define PVC annotations in the parameters field of StorageClass. When compiling a YAML file, you only need to specify storageClassName.

For example, you can define SAS EVS disk and SSD EVS disk as a storage class, respectively. If a storage class named csi-disk-sas is defined, it is used to create SAS storage.

Custom Storage Class

When a user migrates services from a self-built Kubernetes cluster or other Kubernetes services to CCE, the storage class used in the original application YAML file is different from that used in CCE. As a result, a large number of YAML files or Helm chart packages need to be modified when the storage is used, which is complex and error-prone.

Create a storage class with the same name as that in the original application YAML file in the CCE centralization. After the migration, you do not need to modify the storageClassName in the application YAML file.

For example, the EVS disk storage class used before the migration is disk-standard. After migrating services to a CCE cluster, you can copy the YAML file of the csi-disk storage class in the CCE cluster, change its name to disk-standard, and create another storage class.

storageClassName must be specified in the YAML file to use the storage. If not, the storage cannot be created.

If you set the default StorageClass in the cluster, you can create storage without specifying the storageClassName in the YAML file.

Specifying a Default Storage Class

Custom Storage Class

This section uses the custom storage class of EVS disks as an example to describe how to define SAS EVS disk and SSD EVS disk as a storage class, respectively. For example, if you define a storage class named csi-disk-sas, which is used to create SAS storage, the differences are shown in the following figure. When compiling a YAML file, you only need to specify storageClassName.

  • 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 reclaim 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 is in the Released status and cannot be bound to the PVC again.

If high data security is required, 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 StorageClass again. The command output is as follows:

# 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-obs             everest-csi-provisioner         17d

Specifying 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

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