When a ZFS system starts going rogue and fills the disk, it would be nice if `sudo` still worked.
I know of quota, reservation, and refreservation.
I've tested with `zfs create -o refreservation=5GB zroot/reservation` etc, but the system still gets to the point of disk space exhaustion and sudo starts getting uppity.
So far, I think the easiest way may be quota.
`zfs set quota=15G zroot/var/log`
That is similar to creating a separate zpool of size 15G and moving /var/log over to that zpool.