OpenShift Container Platform

Enabling KubeVirt VM image caching

To optimize both cluster startup time and storage usage, you can use KubeVirt virtual machine (VM) image caching.

KubeVirt VM image caching supports the use of a storage class that is capable of smart cloning and the ReadWriteMany access mode. For more information about smart cloning, see "Cloning a data volume using smart-cloning".

Image caching works as follows:

The VM image is imported to a persistent volume claim (PVC) that is associated with the hosted cluster.
A unique clone of that PVC is created for every KubeVirt VM that is added as a worker node to the cluster.

Image caching reduces VM startup time by requiring only a single image import. It can further reduce overall cluster storage usage when the storage class supports copy-on-write cloning.

Procedure

To enable image caching, during cluster creation, use the --root-volume-cache-strategy=PVC argument by running a command as shown in the following example:
```
$ hcp create cluster kubevirt \
  --name my-hosted-cluster \
  --node-pool-replicas 2 \
  --pull-secret /user/name/pullsecret \
  --memory 8Gi \
  --cores 2 \
  --root-volume-cache-strategy=PVC
```
- --name specifies the name of your hosted cluster.
- --node-pool-replicas specifies the worker count.
- --pull-secret specifies the path to your pull secret.
- --memory specifies a value for memory.
- --cores specifies a value for CPU.
- --root-volume-cache-strategy specifies a strategy for image caching.