I have figured it out. not sure why I did not see this answer earlier. What you do is edit the<vmid.conf> file
and after the disks you don't want to be backed up , add ,backup=no. Here is part of my conf file.
scsi1: /dev/disk/by-uuid/15123ffd-956a-426b-8afb-ee7cd4a4e5bd,size=500G,backup=no
scsi2: /dev/disk/by-uuid/79f9fbc5-b127-425c-9f79-fccafe842e8b,size=500G,backup=no
very simple.