hi,
when creating a datablock, you end up with a raw image. If you want to use it as a startup disk, you should change the type from “datablock” to “OS”. Under FSTYPE you mention qcow2, but that should be something else, like ext4 or ntfs.
If you want to use qcow2 images, don’t create datablocks, but use qemi-img to create qcow2 images and then import them to the datastore. (and make sure to use the prefix “vd” instead of “sd”, so it uses virtio).
This thread: RAW vs QCOW2 images; VMs fail
contains ways to create qcow2 images, or convert your existing raw images to qcow2.
hope this helps !