I run FreeBSD ZFS on my desktop and have for years, and we're thinking of using it (for the root fs) at work. I considered the ZOL integration to be good news. We'll get better CI, and we'll share features with ZOL faster. I don't really see the downside.
I've also run ZOL for 7 years on my wife's desktops..
Sadly, FreeBSD (and Illumos) are now defacto downstreams, since a lot of the active ZFS work is now happening on Linux. That's a sad fact, but true, and sticking our heads in the sand won't change it. (and may, in fact, make it worse).
My understanding from the message, and from talking to the devs involved is that integration with ZOL will make FreeBSD an equal partner. FreeBSD will be included in the CI, so that ZOL changes that break FreeBSD cannot be merged. Changes originating in FreeBSD will also be merged faster to Linux, and with review from the original author to make sure they are merged correctly. Eg, it is better for everybody (except perhaps the folks left on Illumos or other Open Solaris forks).
During last month's openzfs call [0], one of the actions items that came up for discussion was "How do we all work together?" There are scenarios where issues on ZoL are still being investigated on Illumos. I don't know further details on this, sorry.
At first came the interesting question of "what is OpenZFS"? A spec? A reference implementation that everyone branches off? How do we exchange fixes and ideas and updates?
Another topic that came up was "What should the defaults for a zpool be?" this was for portable zpools.
Please note: the above were still open questions. We're going to have a few follow up calls to understand and ideate better.
Source: I was on the call, and I'm an Illumos community member.
I just wanted to add: the real challenges are figuring out what it means to have a shared code base across oppressing systems for a file system. This is not like openssh. The porting, verification and feature parity checks are unique and challenging to solve.
ZoL may have more development activity behind it, but due to licencing, it will never be a first-class citizen in Linux like it is on FreeBSD/Illumos. That limitation makes the decision to turn OpenZFS (essentially, ZoL) into the upstream seem unwise.
Honestly, due to the licensing it's not exactly a first-class citizen on FreeBSD either. It's a copyleft license that doesn't pollute other source files, but it's still copyleft for ZFS itself. That is contra to the BSD license.
Integration of ZFS will always be an issue in any platform that is not licensed under Sun’s CDL license. To run ZFS, FreeBSD developers had to effectively build a kernel module that paravirtualises the OpenSolaris kernel. So there will always be integration work. The new upstream rebase should make integration much more smooth and allow for features to be released more quickly to FreeBSD than we have been able to do previously.
It really doesn’t get the recognition it desires. It’s has highly advanced features and performance and frankly more people should be using it.
Given the recent ZFS/FreeBSD news - I’d love more people to adopt DragonflyBSD for its Hammer2 filesysten.
[1] https://news.ycombinator.com/item?id=15484735