There's a reason the other major non-debian distros have switched to it by default.
I'm still waiting for ubuntu to allow installing using btrfs + fulldisk encryption by default, which is currently a massive issue.
Not sure where you got this from. OpenZFS on Linux is considered stable by the project. It has been rock solid, free of major issues, and considered more than ready for prime time since at least 0.8, and probably much earlier. It’s now at 2.1.
I’ve been using it across multiple environments, including my personal laptop and workstation which maintained the same root-on-ZFS install for 6+ years, including 2 full migrations to new hardware using zfs send. I’ve deployed much larger pools in professional settings and they’ve been rock solid.
Btrfs has had numerous data loss issues in that time. I can only recall one data loss issue in a ZFS on Linux release, several years ago, which was caught very quickly.
Btrfs hasn't had any major data loss issues for the last 5 years (excluding the raid issues) btrfs is much newer than ZFS, so obviously it took longer to be stable, if you're talking about 6+ years ago, Btrfs was obviously not ready yet, but now? It's been the default on OpenSUSE for 5 years and Fedora for 2.
“I can’t believe Nixon won. I don’t know anyone who voted for him.” -- Pauline Kael
I use ZFS on root. Know lots of people who do. Might be your bubble?
That says more about the distributions than about ZFS’s fitness or maturity as a file system.
It’s understandable that many distributions don’t bundle ZFS, since the licensing is still an open debate. Although that’s not so cut-and-dried [1], I wouldn’t expect broad support from distributions unless and until these issues have been tested and proved out one way or the other. No organization wants to insert themselves into a legal skirmish.
The best (and probably only good thing) to come out of Ubuntu’s support for ZFS is the vote of confidence in favor of ZFS’s legality in-base from a major corporate entity. We can hope more distributions pick up on this, but I’m not holding my breath.
But legal issues and technicalities say nothing at all about the relative technical merit of ZFS (or any other file system).
> how many people use it as a filesystem for the linux root? Never seen anyone putting the main OS on zfs
Quite a lot of users, actually. There’s a significant community around ZFS, including an ecosystem of some robust tooling. ZFSBootMenu is evidence enough that people want to run root on ZFS, and that root on ZFS is both feasible and highly desirable. Compare its feature list to what you can achieve with root-on-Btrfs, and ZFS pretty handily comes out ahead as the more powerful file system in terms of real world administrative capabilities.
[1] https://blog.hansenpartnership.com/are-gplv2-and-cddl-incomp...
Although I'd still suggest single-block-device-btrfs on mdadm instead. The per-file RAID in btrfs (/zfs) can skip over unallocated sectors, but mdadm gets to do larger sequential writes with less random seeking. On spinning disks this can very quickly overtake the performance at even lightly filled volumes.