Storage on OpenShift Virtualization Training

Mounting storage

Mon, 01 Jan 0001 00:00:00 +0000

There are multiple ways of mounting a disk to a virtual machine. In this section we will mount various disks to our VM.

Kubernetes storage

There are multiple methods to provide storage for your virtual machines. For storage to be attached you have to specify a volume in the spec.templates.spec.volumes block of your virtual machine. This volume must then be referenced as a device in spec.templates.spec.domain.devices.disks or spec.templates.spec.domain.devices.filesystems.

A sample configuration of a PersistentVolumeClaim mounted as a disk:

Using StorageProfiles

Mon, 01 Jan 0001 00:00:00 +0000

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 OpenShift Virtualization.

Warning

Due to the cluster-wide configuration of storage classes, the resources and commands in this lab are not meant to be created and executed!

What are storage profiles

For each available StorageClass, OpenShift Virtualization 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.

Hotplugging disks

Mon, 01 Jan 0001 00:00:00 +0000

In this section we will hotplug a disk to a running virtual machine.

Task 6.3.1: Starting a virtual machine

First, create a file vm_lab06-cirros.yaml in the folder labs/lab06 and start with the following virtual machine definition:

apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
 name: lab06-cirros
spec:
 runStrategy: Halted
 template:
 metadata:
 labels:
 kubevirt.io/domain: lab06-volume
 spec:
 domain:
 devices:
 disks:
 - name: rootdisk
 disk:
 bus: virtio
 - name: cloudinitdisk
 disk:
 bus: virtio
 interfaces:
 - name: default
 masquerade: {}
 resources:
 requests:
 memory: 64M
 networks:
 - name: default
 pod: {}
 volumes:
 - name: rootdisk
 containerDisk:
 image: quay.io/kubevirt/cirros-container-disk-demo
 - name: cloudinitdisk
 cloudInitNoCloud:
 userData: |
 #cloud-config

Create and start the virtual machine with:

VM snapshot and restore

Mon, 01 Jan 0001 00:00:00 +0000

OpenShift Virtualization provides a snapshot and restore functionality. This feature is only available if your storage driver supports VolumeSnapshots and a VolumeSnapshotClass is configured.

You can list the available VolumeSnapshotClass with:

oc get volumesnapshotclass --namespace lab-<username>

NAME DRIVER DELETIONPOLICY AGE
longhorn-snapshot-vsc driver.longhorn.io Delete 21d

You can snapshot virtual machines in running or stopped state. Using the QEMU guest agent the snapshot can temporarily freeze your VM to get a consistent backup.

Resizing a Disk

Mon, 01 Jan 0001 00:00:00 +0000

In this section we will resize the root disk of a virtual machine.

Requirements

Resizing disks depends on the Kubernetes storage provider. The CSI driver must support resizing volumes and must be configured with AllowVolumeExpansion.

Further, it may depend on the operating system you use. Whenever the volume is resized, your VM might see the change in disk size immediately. But there might still be the need to resize the partition and filesystem. Fedora Cloud for instance has the package cloud-utils-growpart installed. This rewrites the partition table so that the partition takes up all the space available. This makes it a very handy choice for resizing disk images.