Currently the default storage interface for VM disks is virtio-blk. Virtio-blk disks consume addresses on the PCI bus and this is an important limitation especially for hotplug. For this reason, hotplug uses virtio-scsi which does not suffer this limitation. Since performance parity has been shown between virtio-blk and virtio-scsi it makes sense to standardize on virtio-scsi. This decision was also made by oVirt without issue.