Storage Class Reference

This page documents DirectPV storage class configuration, including the default storage class and how to create custom storage classes.

DirectPV installs a default storage class named directpv-min-io.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: directpv-min-io
  labels:
    application-name: directpv.min.io
    application-type: CSIDriver
    directpv.min.io/created-by: kubectl-directpv
    directpv.min.io/version: v1beta1
  finalizers:
    - foregroundDeletion
provisioner: directpv-min-io
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
allowedTopologies:
  - matchLabelExpressions:
      - key: directpv.min.io/identity
        values:
          - directpv-min-io
parameters:
  csi.storage.k8s.io/fstype: xfs

DirectPV uses WaitForFirstConsumer volume binding mode. This mode delays volume binding and provisioning until a pod using the PersistentVolumeClaim is created.

This behavior ensures:

• PersistentVolumes are provisioned on nodes matching the pod’s scheduling constraints.
• Topology-aware scheduling based on resource requirements, node selectors, pod affinity/anti-affinity, and taints/tolerations.
• Optimal data locality for direct-attached storage.

Create custom storage classes to control drive selection using labels.

Use the create-storage-class.sh script:

create-storage-class.sh <NAME> <DRIVE-LABELS>...

Create a fast tier storage class:

create-storage-class.sh fast-tier-storage 'directpv.min.io/tier: fast'

Create a thick provisioning storage class:

create-storage-class.sh directpv-thick-provisioning 'directpv.min.io/skip-thin-provisioning: "true"'

Create a storage class with multiple labels:

create-storage-class.sh nvme-hot-storage 'directpv.min.io/tier: hot' 'directpv.min.io/drive-type: nvme'

Reference the custom storage class in your PersistentVolumeClaim:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  volumeMode: Filesystem
  storageClassName: fast-tier-storage
  accessModes: ["ReadWriteOnce"]
  resources:
    requests:
      storage: 8Mi

Custom storage classes use parameters to select specific drives.

Label drives with access tiers to categorize by performance:

Label drives with an access tier:

kubectl directpv label drives --drives=nvme1n1 directpv.min.io/access-tier=hot

Create storage class for hot tier:

create-storage-class.sh hot-tier-storage 'directpv.min.io/access-tier: hot'

By default, DirectPV uses thin provisioning. Volumes are provisioned based on the requested size, regardless of the drive’s actual free capacity.

To use thick provisioning, create a storage class with skip-thin-provisioning:

create-storage-class.sh thick-storage 'directpv.min.io/skip-thin-provisioning: "true"'

With thick provisioning, volumes are provisioned based on the actual free capacity available on drives.

When a pod requests a PersistentVolume, DirectPV selects a drive using this process:

1. Validate the filesystem type is xfs.
2. Validate the access tier if specified.
3. Check for existing volume in DirectPVDrive CRD objects. If found, schedule the first drive containing the volume.
4. If no existing volume, filter drives by:
   • Requested capacity
   • Access tier (if requested)
   • Topology constraints (if requested)
   • Custom labels (if using custom storage class)
5. If multiple drives match, select the drive with the greatest free capacity.
6. If multiple drives have equal free capacity, select one randomly.

If no drives match the criteria, DirectPV returns an error and Kubernetes retries the request.

The following label keys are reserved and cannot be used for custom drive labels:

• directpv.min.io/node
• directpv.min.io/drive-name
• directpv.min.io/drive
• directpv.min.io/access-tier
• directpv.min.io/version
• directpv.min.io/created-by
• directpv.min.io/pod.name
• directpv.min.io/pod.namespace
• directpv.min.io/pod.statefulset
• directpv.min.io/identity
• directpv.min.io/rack
• directpv.min.io/zone
• directpv.min.io/region
• directpv.min.io/migrated
• directpv.min.io/request-id
• directpv.min.io/suspend
• directpv.min.io/image-tag
• directpv.min.io/skip-thin-provisioning