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Configuring local storage by using the hostpath provisioner

You can configure local storage for virtual machines by using the hostpath provisioner (HPP).

When you install the OKD Virtualization Operator, the Hostpath Provisioner Operator is automatically installed. HPP is a local storage provisioner designed for OKD Virtualization that is created by the Hostpath Provisioner Operator. To use HPP, you create an HPP custom resource (CR) with a basic storage pool.

Creating a hostpath provisioner with a basic storage pool

You configure a hostpath provisioner (HPP) with a basic storage pool by creating an HPP custom resource (CR) with a storagePools stanza. The storage pool specifies the name and path used by the CSI driver.

Do not create storage pools in the same partition as the operating system. Otherwise, the operating system partition might become filled to capacity, which will impact performance or cause the node to become unstable or unusable.
Prerequisites

  • The directories specified in spec.storagePools.path must have read/write access.

Procedure

  1. Create an hpp_cr.yaml file with a storagePools stanza as in the following example:

    apiVersion: hostpathprovisioner.kubevirt.io/v1beta1
kind: HostPathProvisioner
metadata:
  name: hostpath-provisioner
spec:
  imagePullPolicy: IfNotPresent
  storagePools: (1)
  - name: any_name
    path: "/var/myvolumes" (2)
workload:
  nodeSelector:
    kubernetes.io/os: linux
    1 The storagePools stanza is an array to which you can add multiple entries.
    2 Specify the storage pool directories under this node path.

  2. Save the file and exit.

  3. Create the HPP by running the following command:

    $ oc create -f hpp_cr.yaml

About creating storage classes

When you create a storage class, you set parameters that affect the dynamic provisioning of persistent volumes (PVs) that belong to that storage class. You cannot update a StorageClass object’s parameters after you create it.

In order to use the hostpath provisioner (HPP) you must create an associated storage class for the CSI driver with the storagePools stanza.

Virtual machines use data volumes that are based on local PVs. Local PVs are bound to specific nodes. While the disk image is prepared for consumption by the virtual machine, it is possible that the virtual machine cannot be scheduled to the node where the local storage PV was previously pinned.

To solve this problem, use the Kubernetes pod scheduler to bind the persistent volume claim (PVC) to a PV on the correct node. By using the StorageClass value with volumeBindingMode parameter set to WaitForFirstConsumer, the binding and provisioning of the PV is delayed until a pod is created using the PVC.

Creating a storage class for the CSI driver with the storagePools stanza

To use the hostpath provisioner (HPP) you must create an associated storage class for the Container Storage Interface (CSI) driver.

When you create a storage class, you set parameters that affect the dynamic provisioning of persistent volumes (PVs) that belong to that storage class. You cannot update a StorageClass object’s parameters after you create it.

Virtual machines use data volumes that are based on local PVs. Local PVs are bound to specific nodes. While a disk image is prepared for consumption by the virtual machine, it is possible that the virtual machine cannot be scheduled to the node where the local storage PV was previously pinned.

To solve this problem, use the Kubernetes pod scheduler to bind the persistent volume claim (PVC) to a PV on the correct node. By using the StorageClass value with volumeBindingMode parameter set to WaitForFirstConsumer, the binding and provisioning of the PV is delayed until a pod is created using the PVC.
Procedure

  1. Create a storageclass_csi.yaml file to define the storage class:

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: hostpath-csi
provisioner: kubevirt.io.hostpath-provisioner
reclaimPolicy: Delete (1)
volumeBindingMode: WaitForFirstConsumer (2)
parameters:
  storagePool: my-storage-pool (3)
    1 The two possible reclaimPolicy values are Delete and Retain. If you do not specify a value, the default value is Delete.
    2 The volumeBindingMode parameter determines when dynamic provisioning and volume binding occur. Specify WaitForFirstConsumer to delay the binding and provisioning of a persistent volume (PV) until after a pod that uses the persistent volume claim (PVC) is created. This ensures that the PV meets the pod’s scheduling requirements.
    3 Specify the name of the storage pool defined in the HPP CR.

  2. Save the file and exit.

  3. Create the StorageClass object by running the following command:

    $ oc create -f storageclass_csi.yaml

About storage pools created with PVC templates

If you have a single, large persistent volume (PV), you can create a storage pool by defining a PVC template in the hostpath provisioner (HPP) custom resource (CR).

A storage pool created with a PVC template can contain multiple HPP volumes. Splitting a PV into smaller volumes provides greater flexibility for data allocation.

The PVC template is based on the spec stanza of the PersistentVolumeClaim object:

Example PersistentVolumeClaim object
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: iso-pvc
spec:
  volumeMode: Block (1)
  storageClassName: my-storage-class
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
1 This value is only required for block volume mode PVs.

You define a storage pool using a pvcTemplate specification in the HPP CR. The Operator creates a PVC from the pvcTemplate specification for each node containing the HPP CSI driver. The PVC created from the PVC template consumes the single large PV, allowing the HPP to create smaller dynamic volumes.

You can combine basic storage pools with storage pools created from PVC templates.

Creating a storage pool with a PVC template

You can create a storage pool for multiple hostpath provisioner (HPP) volumes by specifying a PVC template in the HPP custom resource (CR).

Do not create storage pools in the same partition as the operating system. Otherwise, the operating system partition might become filled to capacity, which will impact performance or cause the node to become unstable or unusable.
Prerequisites

  • The directories specified in spec.storagePools.path must have read/write access.

Procedure

  1. Create an hpp_pvc_template_pool.yaml file for the HPP CR that specifies a persistent volume (PVC) template in the storagePools stanza according to the following example:

    apiVersion: hostpathprovisioner.kubevirt.io/v1beta1
kind: HostPathProvisioner
metadata:
  name: hostpath-provisioner
spec:
  imagePullPolicy: IfNotPresent
  storagePools: (1)
  - name: my-storage-pool
    path: "/var/myvolumes" (2)
    pvcTemplate:
      volumeMode: Block (3)
      storageClassName: my-storage-class (4)
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 5Gi (5)
  workload:
    nodeSelector:
      kubernetes.io/os: linux
    1 The storagePools stanza is an array that can contain both basic and PVC template storage pools.
    2 Specify the storage pool directories under this node path.
    3 Optional: The volumeMode parameter can be either Block or Filesystem as long as it matches the provisioned volume format. If no value is specified, the default is Filesystem. If the volumeMode is Block, the mounting pod creates an XFS file system on the block volume before mounting it.
    4 If the storageClassName parameter is omitted, the default storage class is used to create PVCs. If you omit storageClassName, ensure that the HPP storage class is not the default storage class.
    5 You can specify statically or dynamically provisioned storage. In either case, ensure the requested storage size is appropriate for the volume you want to virtually divide or the PVC cannot be bound to the large PV. If the storage class you are using uses dynamically provisioned storage, pick an allocation size that matches the size of a typical request.

  2. Save the file and exit.

  3. Create the HPP with a storage pool by running the following command:

    $ oc create -f hpp_pvc_template_pool.yaml