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 OpenShift Virtualization Operator, the Hostpath Provisioner Operator is automatically installed. HPP is a local storage provisioner designed for OpenShift 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.

Prerequisites

• The directories specified in spec.storagePools.path must have read/write access.
• You have installed the OpenShift CLI (oc).

Procedure

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

   apiVersion: hostpathprovisioner.kubevirt.io/v1beta1
   kind: HostPathProvisioner
   metadata:
     name: hostpath-provisioner
   spec:
     imagePullPolicy: IfNotPresent
     storagePools:
     - name: any_name
       path: "/var/myvolumes"
     workload:
       nodeSelector:
         kubernetes.io/os: linux

   • spec.storagePools.name defines the name to identify the source to use. It must be the same as the storagePools name in the StorageClass.yaml.
   • spec.storagePools.path defines the storage pool directories under this node path. Ensure that the path /var/myvolumes value specifies a directory that exists on each worker node.
2. Save the file and exit.
3. Create the HPP by running the following command:
   terminal

   $ 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.

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

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.

Procedure

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

   apiVersion: storage.k8s.io/v1
   kind: StorageClass
   metadata:
     name: hostpath-csi
   provisioner: kubevirt.io.hostpath-provisioner
   reclaimPolicy: Delete
   volumeBindingMode: WaitForFirstConsumer
   parameters:
     storagePool: my-storage-pool

   • reclaimPolicy defines whether the underlying storage is deleted or retained when a user deletes a PVC. The two possible reclaimPolicy values are Delete and Retain. If you do not specify a value, the default value is Delete.
   • volumeBindingMode defines the timing of PV creation. In this example, the WaitForFirstConsumer configuration delays PV creation until the scheduler assigns a pod to a specific node.
     Note

     Virtual machines use data volumes based on local PVs, which reside on specific nodes. When the system prepares a disk image for the virtual machine, the scheduler might not place the virtual machine on the node where it pinned the local storage PV. + To solve this problem, use the Kubernetes pod scheduler to bind the persistent volume claim (PVC) to a PV on the correct node. Setting the volumeBindingMode parameter of the StorageClass to WaitForFirstConsumer delays PV binding and provisioning until you create a pod that uses the PVC.

   • parameters.storagePool defines the name of the storage pool defined in the HPP custom resource (CR).
2. Save the file and exit.
3. Create the StorageClass object by running the following command:
   terminal

   $ 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:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: iso-pvc
spec:
  volumeMode: Block
  storageClassName: my-storage-class
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi

The spec.volumeMode value is only required for block volume mode PVs.

You define a storage pool by 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 persistent volume claim (PVC) template in the HPP custom resource (CR).

Prerequisites

• The directories specified in spec.storagePools.path must have read/write access.
• You have installed the OpenShift CLI (oc).

Procedure

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

   apiVersion: hostpathprovisioner.kubevirt.io/v1beta1
   kind: HostPathProvisioner
   metadata:
     name: hostpath-provisioner
   spec:
     imagePullPolicy: IfNotPresent
     storagePools:
     - name: my-storage-pool
       path: "/var/myvolumes"
       pvcTemplate:
         volumeMode: Block
         storageClassName: my-storage-class
         accessModes:
         - ReadWriteOnce
         resources:
           requests:
             storage: 5Gi
     workload:
       nodeSelector:
         kubernetes.io/os: linux

   • spec.storagePools defines an array that can contain both basic and PVC template storage pools.
   • spec.storagePools.path defines the storage pool directories under this node path.
   • spec.storagePools.pvcTemplate.volumeMode is an optional parameter, which can be either Block or Filesystem if 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.
   • spec.storagePools.pvcTemplate.storageClassName specifies 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.
   • spec.storagePools.pvcTemplate.resources.requests.storage defines the storage request for statically or dynamically provisioned storage. 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 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:
   terminal

   $ oc create -f hpp_pvc_template_pool.yaml