Correction, parted_devies does detect block devices but does not distinguish virtual hard drives from cdroms:
$ sudo parted_devices /dev/vda 2147483648 Virtio Block Device /dev/vdb 693774336 Virtio Block Device
Correction, parted_devies does detect block devices but does not distinguish virtual hard drives from cdroms:
$ sudo parted_devices
/dev/vda 2147483648 Virtio Block Device
/dev/vdb 693774336 Virtio Block Device