6.2. Using StorageProfiles

When working with storage and the containerized data importer, one usually wants to have meaningful defaults. Let us have a look at how we can configure storage profiles to be used with KubeVirt.

What are storage profiles

For each available StorageClass, KubeVirt creates a StorageProfile resource. StorageProfiles serve as a source of information about the recommended parameters for a PVC. They are used when provisioning a PVC using a DataVolume. Having recommended parameters defined centrally in a StorageProfile reduces the complexity of your DataVolume definition.

You can check the StorageProfiles with:

kubectl get storageprofiles --namespace lab-<username>

NAME             AGE
hcloud-volumes   38d
longhorn         38d

You may check the configuration of the StorageProfile with:

kubectl describe storageprofile longhorn --namespace lab-<username>

Name:         longhorn
Namespace:    
Labels:       app=containerized-data-importer
              app.kubernetes.io/component=storage
              app.kubernetes.io/managed-by=cdi-controller
              cdi.kubevirt.io=
Annotations:  <none>
API Version:  cdi.kubevirt.io/v1beta1
Kind:         StorageProfile
Metadata:
  Creation Timestamp:  2024-07-27T07:54:21Z
  Generation:          2
  Owner References:
    API Version:           cdi.kubevirt.io/v1beta1
    Block Owner Deletion:  true
    Controller:            true
    Kind:                  CDI
    Name:                  cdi
    UID:                   a9f271d9-e57a-4199-b61d-28dd6925587c
  Resource Version:        16172528
  UID:                     5ebfeeb1-c45d-44b6-8d48-d31cfc501110
Spec:
Status:
  Clone Strategy:                  snapshot
  Data Import Cron Source Format:  pvc
  Provisioner:                     driver.longhorn.io
  Snapshot Class:                  longhorn-snapshot-vsc
  Storage Class:                   longhorn
Events:                            <none>

Create a DataVolume

Let’s have a look how this works. Assume we create a DataVolume my-dv with the following specification and apply it to the cluster:

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
metadata:
  name: my-dv
spec:
  source:
    blank: {}
  storage:
    resources:
      requests:
        storage: 128Mi

The DataVolume will not be created. Describe the DataVolume with:

kubectl describe datavolume my-dv --namespace lab-<username>

We see that CDI is lacking some information to create the PVC and returns an error:

Status:
  Conditions:
    Message:               no accessMode defined on StorageProfile for longhorn StorageClass
    Reason:                ErrClaimNotValid
    Status:                Unknown

This means that the controller did not know which access mode to use for the PVC.

Define StorageProfiles

Besides others, a storage profile spec block can take the following parameters:

• claimPropertySets
  • accessMode - Contains the desired access modes the volume should have
  • volumeMode - Defines what type of volume is required by the claim
• cloneStrategy - Defines the preferred method for performing a CDI clone
  • copy - Copy blocks of data over the network
  • snapshot - Clones the volume by creating a temporary VolumeSnapshot and restores it to a new PVC
  • csi-clone - Clones the volume using a CSI clone

If you want to read more about parameters, defaults and how storage profiles are used, check the StorageProfiles documentation .

Setting AccessMode and VolumeMode

To fix the issue above and provide default values for the storage profile longhorn, we can set defaults in the spec block of the storage profile.

Let’s assume we add the accessMode and volumeMode to the longhorn storage profile like this:

apiVersion: cdi.kubevirt.io/v1beta1
kind: StorageProfile
metadata:
  name: longhorn
[...]
spec:
  claimPropertySets:
    - accessModes:
      - ReadWriteOnce
      volumeMode: Filesystem
[...]

As soon as we have the storage profile configured and in place, we can re-apply our DataVolume:

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
metadata:
  name: my-dv
spec:
  source:
    blank: {}
  storage:
    resources:
      requests:
        storage: 128Mi

It is now successfully provisioned using the defaults from the storage profile:

kubectl describe datavolume my-dv --namespace lab-<username>

Status:
  Conditions:
    Message:               PVC my-dv Bound
    Reason:                Bound
    Status:                True