After consulting with Jamie, we reached the conclusion that the reason why the root of FB1 is so huge is because of the way the RAID for /frames is setup. Based on my googling, I couldn't find a way to exclude the nfs stuff while doing a backup using dd, which isn't all that surprising because dd is supposed to make an exact replica of the disk being cloned, including any empty space. So we don't have that flexibility with dd. The advantage of using dd is that if it works, we have a plug-and-play clone of the boot disk and root filesystem which we can use in the event of a hard-disk failure.

1. One option would be to stop all the daqd processes, unmount /frames, and then do a dd backup of the true boot disk and root filesystem.
2. Another option would be to use rsync to do the backup - this way we can selectively copy the files we want and ignore the nfs stuff. I suspect this is what we will have to do for the second layer of backup we have planned, which will be run as a daily cron job. But I don't think this approach will give us a plug-and-play replacement disk in the event of a disk failure.
3. Third option is to use one of the 2TB HGST drives, and just do a dd backup - some of this will be /frames, but that's okay I guess.