That's great for instances that use volumes. I think the OP wanted to know how to back up instances that use ephemeral storage while the instance continues running (and so do I :).

I think to make a backup of the ephemeral disk we will need to create a snapshot of instance itself. The resulting snapshot in this case will be a openstack image type.Can use below command as well openstack server image create --name <snapshot_name> <server>(Server name or ID).Not sure though :P

Our storage backend is Ceph, and we run weekly backups without interruptions of the running instances, but this is done on the rbd layer (rbd export <nova_id>_disk...). This is the best solution for us as doing a nova snapshot (dashboard or CLI) would result in a new glance image every time.

Additionally, you can set

[workarounds]
disable_libvirt_livesnapshot = false

on compute nodes (nova.conf) to enable live snapshots with nova. This should prevent the instances from freezing.

This is the actual answer. Just a note: Setting it to false carries risks as described in https://docs.openstack.org/nova/pike/....