When I use sudo zfs get all, I see that both my old pool (data) and my newly created pool (backup) are on version 5, which I think refers to the zfs version, not the zpool version.

The amount of space used in a zpool on one of my machines is considerably larger than the space in the zfs filesystems added up. I can't figure out what's going on. Code: remotebackup# zfs list -t all ...