Managing storage classes

Storage class (StorageClass) allows administrators to divide the stores they provision into classes with defined parameters. Classes vary by disk type and pricing policy.

Managed Service for Kubernetes has the following storage classes available that differ by the disk type:

• yc-network-hdd (default): Network HDD storage (network-hdd).
• yc-network-ssd: Network SSD storage (network-ssd).
• yc-network-ssd-nonreplicated: Improved-performance non-replicated SSD storage (network-ssd-nonreplicated).
• yc-network-ssd-io-m3: Improved-performance network SSD storage (network-ssd-io-m3).

Each storage is created with the following parameters:

• Volume Binding Mode: WaitForFirstConsumer.
• Reclaim Policy: Delete.

These classes allow you to use PersistentVolumeClaim and PersistentVolume only in ReadWriteOnce access mode.

You can create your own storage class as well as change the default storage class.

Before you start, install kubectl and configure it to work with the created Managed Service for Kubernetes cluster.

Create a storage classCreate a storage class

1. Save the storage class creation specification in the my-sc-hdd.yaml YAML file:

   Learn more about the storage class creation specification format.

   kind: StorageClass
   apiVersion: storage.k8s.io/v1
   metadata:
     name: my-sc-hdd
   provisioner: disk-csi-driver.mks.ycloud.io
   volumeBindingMode: WaitForFirstConsumer
   parameters:
     type: network-hdd
     csi.storage.k8s.io/fstype: ext4
   allowVolumeExpansion: false
   reclaimPolicy: Retain
   

2. Run this command:

   kubectl create -f my-sc-hdd.yaml
   

   Result:

   storageclass.storage.k8s.io/my-sc-hdd created
   

3. Check that the storage class was created:

   kubectl get storageclass
   

   Result:

   NAME                      PROVISIONER                    AGE
   my-sc-hdd                 disk-csi-driver.mks.ycloud.io  76s
   yc-network-hdd (default)  disk-csi-driver.mks.ycloud.io  16m
   yc-network-ssd            disk-csi-driver.mks.ycloud.io  16m
   

Create a storage class specification formatCreate a storage class specification format

Each StorageClass object contains parameters, allowVolumeExpansion, and reclaimPolicy, which are used for dynamic PersistentVolume object allocation.

YAML file structure:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: <storage_class_name> # Used for accessing the storage class.
provisioner: <provider_name>
volumeBindingMode: WaitForFirstConsumer
parameters: # Storage class parameters.
  type: <disk_type>
  csi.storage.k8s.io/fstype: < file_system_type>
allowVolumeExpansion: <enable_volume_expansion>
reclaimPolicy: <reclaim_policy>

Acceptable parameter values include:

• parameters:
  • type: network-hdd, network-ssd, network-ssd-nonreplicated, or network-ssd-io-m3.
  • csi.storage.k8s.io/fstype: ext2, ext3, or ext4.
• reclaimPolicy: Retain or Delete.
• allowVolumeExpansion: true or false.

Change the default storage classChange the default storage class

1. Check which storage class is assigned by default: default is shown next to its name in parentheses.

   kubectl get storageclass
   

   Result:

   NAME                      PROVISIONER                    AGE
   my-sc-hdd                 disk-csi-driver.mks.ycloud.io  76s
   yc-network-hdd (default)  disk-csi-driver.mks.ycloud.io  16m
   yc-network-ssd            disk-csi-driver.mks.ycloud.io  16m
   

2. Change the storageclass.kubernetes.io/is-default-class parameter of the default storage class to false, to remove its status as the default class:

   kubectl patch storageclass yc-network-hdd \
     -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"false"}}}'
   

3. Check that yc-network-hdd is no longer the default storage class:

   kubectl get storageclass
   

   Result:

   NAME            PROVISIONER                    AGE
   my-sc-hdd       disk-csi-driver.mks.ycloud.io  2m36s
   yc-network-hdd  disk-csi-driver.mks.ycloud.io  17m
   yc-network-ssd  disk-csi-driver.mks.ycloud.io  17m
   

4. Specify a new default storage class, e.g., my-sc-hdd:

   kubectl patch storageclass my-sc-hdd \
     -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'
   

5. Check that my-sc-hdd is the default storage class:

   kubectl get storageclass
   

   Result:

   NAME                 PROVISIONER                    AGE
   my-sc-hdd (default)  disk-csi-driver.mks.ycloud.io  4m21s
   yc-network-hdd       disk-csi-driver.mks.ycloud.io  19m
   yc-network-ssd       disk-csi-driver.mks.ycloud.io  19m