I think I have #ZFS not killing my RAM now, but uh, it's slow as fuck now.

I am sending a #ZFS on #FreeBSD dataset to a USB disk (which doesn't have a copy of that dataset), using
zfs send -v zroot/dataset@back | zfs recv usb_disk/dataset

It's taking more RAM than the size of the dataset (and eventually... crashing the process instead of swapping)