Unable to take snapshot with Ceph image DS + Deploy mode SSH

Hello,
we have a ceph image_ds, some images downloaded from OpenNebula Public on it
We are deploying the VMs using KVM and TM_MAD_SYSTEM = “ssh”
We can’t take snapshot of the vms running this way. This is the error:
error: unsupported configuration: internal snapshot for disk sda unsupported for storage type raw

I know that ceph uses raw format, but the images are deployed locally on the hosts.
These are some parameters taken from the image page:
Name CentOS 7 - KVM
Datastore cephds
DEV_PREFIX vd
FORMAT qcow2
FROM_APP 30
FROM_APP_NAME CentOS 7 - KVM
TM_MAD_SYSTEM SSH

There is a way to be able to take snapshots?
Thank you
Marco