Ahoy !
From another thread I was informed about this old incomplete port of ZFS filesystem. The unfinished port.was done by a GSoC project.
Is someone actually interested in the ZFS filesystem port completion for Haiku ?
HERE is >>>-------------> GitHub - s3thi/zfs-haiku: ZFS port for Haiku.
the work done then in the past – so that is available until now – if you would contribute on it
I picked up just to be on the map … as it was new for me – how much incomplete developments for Haiku can be ? 
EDIT : fixed some sentences,
and
linked the development stuff from that another thread
( thanks to @extrowerk ).