That zfs needs so much RAM is a myth that can be easily refuted. Start a Linux VM with hardly any RAM and let zfs run on it. Works great. There are also sources for this since years: https://www.reddit.com/r/DataHoarder/comments/3s7vrd/so_you_...
(if you don't have any files) Doesn't do me much good with my 10TB's of data.