StorageClass

Introduction

A StorageClass in Kubernetes is a resource that categorizes storage types in a cluster. It can also serve as a configuration template for creating PVs. When creating a PVC or PV, you must specify a StorageClass. This resource object defines the storage mode and configuration parameters for dynamic volume provisioning, such as volume type, access mode, and volume lifecycle policy.

When creating a PVC, you only need to specify the StorageClassName. Kubernetes will then automatically create the PVs and underlying storage based on the StorageClass. This greatly reduces the need for manual creation and maintenance of PVs.

In addition to the default StorageClasses provided by CCE, you can customize StorageClasses. For details, see Application Scenarios of Custom Storage.

Creating a StorageClass Using a YAML File

As of now, CCE provides StorageClasses 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.

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

# 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 delay
csi-nas             everest-csi-provisioner         17d          # SFS 1.0
csi-obs             everest-csi-provisioner         17d          # OBS
csi-sfsturbo        everest-csi-provisioner         17d          # SFS Turbo

Each StorageClass contains the default parameters used for dynamically creating a PV. The following is an example of StorageClass 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: When a PVC is deleted, its associated underlying storage resources will be deleted and the PV resources will be removed. Exercise caution if you select this option. Retain: When a PVC is deleted, both of the PV and its associated underlying storage resources will be retained and the PV is marked as released. If you manually delete the PV afterwards, the underlying storage resources will not be deleted. To bind the PV to a new PVC, you need to remove the original binding information from the PV.
allowVolumeExpansion	Specifies whether the PV of this StorageClass 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: After a PVC is created, the storage resources and PV will be created and associated with the PVC without delay. WaitForFirstConsumer: After a PVC is created, it will not be immediately bound to a PV. Instead, the storage resources and PV will be generated and bound to the PVC only after the pod that requires the PVC is scheduled.
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.
	SFS Turbo	csi.storage.k8s.io/csi-driver-name	Yes	Driver type. If SFS Turbo is used, the parameter value is fixed at sfsturbo.csi.everest.io.
		csi.storage.k8s.io/fstype	Yes	If SFS Turbo is used, the value can be nfs.
everest.io/share-access-to		Yes	VPC ID of the cluster.
everest.io/share-expand-type		No	Extension type. The default value is bandwidth, indicating an enhanced file system. This parameter does not take effect.
everest.io/share-source		Yes	The parameter value is fixed at sfs-turbo.
everest.io/share-volume-type		No	SFS Turbo StorageClass. The default value is STANDARD, indicating standard and standard enhanced editions. This parameter does not take effect.
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: a parallel file system s3fs: object bucket
	everest.io/obs-volume-type	Yes	OBS StorageClass. 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 StorageClass, respectively. If a StorageClass named csi-disk-sas is defined, it is used to create SAS storage.	Scenario 1: Specifying the Disk Type in a StorageClass
When a user migrates services from an on-premises Kubernetes cluster or other Kubernetes services to CCE, the StorageClass 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 StorageClass with the same name as that in the original application YAML file in the CCE cluster. After the migration, you do not need to modify the StorageClassName in the application YAML file. For example, the EVS disk StorageClass used before the migration is disk-standard. After migrating services to a CCE cluster, you can copy the YAML file of the csi-disk StorageClass in the CCE cluster, change its name to disk-standard, and create another StorageClass.	Scenario 1: Specifying the Disk Type in a StorageClass
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.	Scenario 2: Specifying the Default StorageClass
When creating storage resources, you must specify an enterprise project. Configuring annotations in each PVC can be a complex process.	Add an enterprise project to a StorageClass. In this case, you do not need to specify an enterprise project when creating a PVC. This is because storage resources will automatically be created in the enterprise project specified in the StorageClass.	Scenario 3: Specifying an Enterprise Project for a StorageClass

Scenario 1: Specifying the Disk Type in a StorageClass

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

Click to enlarge

You can customize a high I/O StorageClass 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 StorageClass, 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 StorageClass, 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 StorageClass, 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, both the PV and underlying storage resources will be retained. You need to manually delete these resources. After the PVC is deleted, the PV is in the Released state and cannot be bound to a 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-nas             everest-csi-provisioner         17d
csi-obs             everest-csi-provisioner         17d
csi-sfsturbo        everest-csi-provisioner         17d

Scenario 2: Specifying the Default StorageClass

You can specify a StorageClass as the default class. In this way, any PVCs created without specifying StorageClassName will automatically use the default StorageClass.

For example, to specify csi-disk-ssd as the default StorageClass, 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"   # Specify the default StorageClass in a cluster. There can only be one default StorageClass per cluster.
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

Run the kubectl create command to create a StorageClass and then check it.

# 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

Scenario 3: Specifying an Enterprise Project for a StorageClass

When creating EVS or OBS PVCs using a StorageClass in CCE, you can specify an enterprise project to assign the created storage resources (EVS disks and OBS) to. This enterprise project can either be the default one or the same one as the cluster belongs to.

If you do not specify any enterprise project, the enterprise project in StorageClass will be used by default. The storage resources created using the CCE's csi-disk or csi-obs StorageClass belong to the default enterprise project.

If you want the storage resources created using a StorageClass to be in the same enterprise project as the cluster, you can customize a StorageClass and specify the enterprise project ID in it.

To use this function, the Everest add-on must be upgraded to v1.2.33 or later.

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: csi-disk-epid      # Customize a StorageClass name.
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/enterprise-project-id: 86bfc701-9d9e-4871-a318-6385aa368183  # Specify the enterprise project ID.
  everest.io/passthrough: 'true'
reclaimPolicy: Delete
allowVolumeExpansion: true
volumeBindingMode: Immediate

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