Bear in mind that many of those who are interested in ZFS are interested in it specifically because they care a lot about not losing data.

With that in mind, let's see what the btrfs wiki has to say about the stability of btrfs:

"Is btrfs stable? Short answer: Maybe."

https://btrfs.wiki.kernel.org/index.php/FAQ#Is_btrfs_stable....

Maybe it's just me, but I'm more than a little concerned by the fact that btrfs has been in development for over 8 years and still doesn't seem to be considered safe to use for storing anything I really care about.

ZFS has a considerable number of very useful features that Btrfs doesn't have. For example, under ZFS, you can delegate administration of a filesystem (subvolume in Btrfs terms) to a normal user. In doing so, you can, for example, set up each user's home directory as its own subvolume, allowing for per-account snapshots, and their own sets of subvolumes which can have differing properties as-needed. ZFS also has support in-driver for sharing volumes, which means nfs shares, and smb shares (unfortunately not under FreeBSD yet) work natively with the filesystem, and can be exported there, instead of needing to muck around with config files and then kicking things in the proper order.

Btrfs is still Not There Yet for a lot of the advantages ZFS has over traditional filesystems. It has a some, and some are half-baked, like its offline deduplication, but is still missing a considerable number. Maybe in five years Btrfs will catch up, but it's not here now.

Rearding licensing, the Linux kernel devs could also relicense to allow for cddl co-existence. Unfortunately, the petulance from such groups as the SFLC makes that very unlikely.

Because ZFS is 100000000000X better than btrfs...

the ZFS commands are more logical, and better designed

The ZFS FileSystem is truely enterprise ready... btrfs is atleast 5 years away from being production ready

btrfs has all kinds of bugs and issues.

zfs did not hold to legacy conventions, they looked at filesystems in a differnet way.

btrfs attempts to hold on the traditional filesystem methodology and shoehorn more modern ideas in to that traditional framework, and IMO it does not work at all

the zfs and zpool commands are brilliant, intuitive, and easy to use.

The btrfs command structure is complicated, non-intuitive, and antiquated

It is comparable in that they are both filesystems... Supposedly the situation has been improving but at least as of months ago compared to zfs performance was horrible, features were lacking, and likelihood of data loss was a lot higher.

> Then again, I've also always been curious why people still keep glamoring over ZFS for Linux when Btrfs exists now, which, as far as I understand, is comparable to ZFS and a fresh implementation (for what that's worth).

My understanding is that Btrfs is still considered less stable than ZFS, or at least has been fairly recently.

> I feel like that ship has sailed since there's Btrfs for Linux too - which also originated at Oracle.

Unfortunately, I think you may be right. It's just sad -- because probably nobody who's anyone at Oracle cares and/or understands.

> Then again, I've also always been curious why people still keep glamoring over ZFS for Linux when Btrfs exists now, which, as far as I understand, is comparable to ZFS and a fresh implementation (for what that's worth).

It is mostly comparable feature-wise, it's just that it hasn't achieved anywhere near the same level of stability for anything other than single-device usage. (At least that's my understanding from following the mailing list for years and years.)