/var/log/ovirt_celery/worker<x>.log
The worker logs contain the status of the disk transfer from the RHV Host to the backup target. Useful if the data transfer process gets stuck or errors in between.
/var/log/ovirt-imageio-daemon/daemon.log
The daemon.log contains all informations about the actual connection between the RHV Host and the backup target. Useful to identify potential connection issues between the RHV Host and Backup target.