Am I right in thinking CHR 6.40.5 doesn't support virtio-scsi as a storage device?
Created a VM in ovirt then copied the downloaded raw image over the HDD image ovirt had created (HDD image ovirt created was also RAW), RouterOS started booting and then decided it couldn't find the HDD.
Changed the Disk from virtio-scsi to virtio and it seemed to work so I'm guessing the CHR is missing the drivers for the virtio-scsi storage device.