There are some interesting comments further in the mail thread from Matthew Ahrens (co-creator of ZFS) and Alan Jude (has recently been working on getting zstan

There are some interesting comments further in the mail thread from Matthew Ahrens (co-creator of ZFS) and Alan Jude (has recently been working on getting zstandard into ZFS) that give more insight. Matthew Ahrens[1]: …Being "upstream" is more a matter of degree than an absolute ordering. In the past, most ZFS features have originated in illumos, and those changes have been ported to the other platforms (notably FreeBSD and ZoL). Looking forward, we see more features originating in ZoL. The OpenZFS community (including FreeBSD) is working to put in place technical processes to ensure that new ZFS features are available on all platforms. The original post in this thread was a proposal for how to do that. Alan Jude[2]: …The way that things have evolved over the last few years means it would be much more difficult to just import changes from ZoL. ZoL was originally far behind the OpenZFS repo, but as they were catching up, they were also fixing bugs and adding features. So there is not really a common point in the source we could start from to import ZoL commit by commit.… The biggest thing to remember is that this is still OpenZFS, and still run by the same developers as it has been. We are just commonizing on the repo that has the most features integrated into it. [1] https://lists.freebsd.org/pipermail/freebsd-current/2018-December/072431.html https://lists.freebsd.org/pipermail/freebsd-current/2018-Dec... [2] https://lists.freebsd.org/pipermail/freebsd-current/2018-December/072430.html https://lists.freebsd.org/pipermail/freebsd-current/2018-Dec...