Configuring Storage

By default, if no advanced configuration is provided, the default storageclass is used for the the KubeVirt VM images, the kubevirt csi mapping, and the etcd volumes.

KubeVirt CSI StorageClass Mapping

KubeVirt CSI permits any infra storage class with the ReadWriteMany access mode to be exposed to the guest cluster. This mapping of infra cluster storage class to guest cluster storage class can be configured during cluster creation using the hcp cli tool and the --infra-storage-class-mapping cli argument.

Below is an example of how to map two infra storage classes called infra-sc1 and infra-sc2 to guest storage classes called guest-sc1 and guest-sc2. Note that --infra-storage-class-mapping argument can be used multiple times within the create command.

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export CLUSTER_NAME=example
export PULL_SECRET="$HOME/pull-secret"
export MEM="6Gi"
export CPU="2"
export WORKER_COUNT="2"

hcp create cluster kubevirt \
--name $CLUSTER_NAME \
--node-pool-replicas $WORKER_COUNT \
--pull-secret $PULL_SECRET \
--memory $MEM \
--cores $CPU \
--infra-storage-class-mapping=infra-sc1/guest-sc1 \
--infra-storage-class-mapping=infra-sc2/guest-sc2

Once the guest cluster is created, the guest-sc1 and guest-sc2 storage classes will be visible within the guest cluster. When users create a PVC within the guest cluster that utilizes one of these storage classes, KubeVirt CSI will facilitate provisioning that volume using the infra storage class mapping that was configured during cluster creation.

KubeVirt VM Root Volume Configuration

The storage class used to host the KubeVirt Virtual Machine root volumes can be configured at cluster creation time using the hcp cli tool and the --root-volume-storage-class argument. Likewise, the size of the volume can be configured using the --root-volume-size cli argument.

Below is an example of setting a custom storage class and volume size for the KubeVirt VMs. The result will be a guest cluster with VMs hosted on 64Gi PVCs hosted by the ocs-storagecluster-ceph-rdb storage class

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export CLUSTER_NAME=example
export PULL_SECRET="$HOME/pull-secret"
export MEM="6Gi"
export CPU="2"
export WORKER_COUNT="2"

hcp create cluster kubevirt \
--name $CLUSTER_NAME \
--node-pool-replicas $WORKER_COUNT \
--pull-secret $PULL_SECRET \
--memory $MEM \
--cores $CPU \
--root-volume-storage-class ocs-storagecluster-ceph-rbd \
--root-volume-size 64

KubeVirt VM Image Caching

KubeVirt VM image caching is an advanced feature that can be used to optimize both cluster startup time and storage utilization. This feature requires the usage of a storage class capable of smart cloning and the ReadWriteMany access mode.

Image caching works by importing the VM image once to a single PVC associated with the HostedCluster, and then making a unique clone of that PVC for every KubeVirt VM added as a worker node to the cluster. This reduces VM startup time by only requiring a single image import, and can further reduce overall cluster storage usage when the storage class supports copy on write cloning.

Image caching can be enabled during cluster creation using the hcp cli tool with the --root-volume-cache-strategy=PVC argument. Below is an example.

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export CLUSTER_NAME=example
export PULL_SECRET="$HOME/pull-secret"
export MEM="6Gi"
export CPU="2"
export WORKER_COUNT="2"

hcp create cluster kubevirt \
--name $CLUSTER_NAME \
--node-pool-replicas $WORKER_COUNT \
--pull-secret $PULL_SECRET \
--memory $MEM \
--cores $CPU \
--root-volume-cache-strategy=PVC

ETCD Storage Configuration

The storage class used to host the etcd data can be customized at cluster creation time using the hcp cli and the --etcd-storage-class cli argument. When no --etcd-storage-class argument is provided, the default storage class will be used.

Below is an example of how to configure usage of a storage class for etcd.

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export CLUSTER_NAME=example
export PULL_SECRET="$HOME/pull-secret"
export MEM="6Gi"
export CPU="2"
export WORKER_COUNT="2"

hcp create cluster kubevirt \
--name $CLUSTER_NAME \
--node-pool-replicas $WORKER_COUNT \
--pull-secret $PULL_SECRET \
--memory $MEM \
--cores $CPU \
--etcd-storage-class="local"