Well, 1st off, he should not be using CIFS from a Linux server. He should be using either NFS or ISCS and using a Linux file system, either EXT4 or XFS.
Set ownership to the urbackup user/group
sudo chown urbackup:urbackup {path to mount point}.
I do this all the time with iSCSI. I like iSCSI as it mounts an actual device instead of a share but NFS should work just fine