“Don’t use ZFS. It’s that simple. It was always more of a buzzword than anything else, I feel, and the licensing issues just make it a non-starter for me.”
This is what Linus Torvalds said in a mailing list to once again express his disliking for ZFS filesystem specially over its licensing.
To avoid unnecessary confusion, this is more intended for Linux distributions, kernel developers and maintainers rather than individual Linux users.
What’s the licensing issue with ZFS and the Linux kernel?
ZFS was open sourced around 2003. This would have meant that Linux distributions start supporting ZFS. But that didn’t really happen because of the complexity of open source licenses.
ZFS is open source under Common Development and Distribution License (CDDL) 1.0 whereas Linux kernel is licensed under the GNU General Public License (GPL) 2.0.
These two open source licenses are not fully compatible with each other. As noted by PCWorld, if ZFS with this license is included in the Linux kernel, this would mean that kernel+ZFS is a derivative work of the (original ZFS-less) Linux kernel.
Torvalds doesn’t trust Oracle
While the whole derivative thing is a matter of debate for legal and licensing experts, Torvalds is skeptical of Oracle. Oracle has a history of suing enterprises for using its code. Remember Oracle vs Android lawsuit over the use of Java?
Other people think it can be ok to merge ZFS code into the kernel and that the module interface makes it ok, and that’s their decision. But considering Oracle’s litigious nature, and the questions over licensing, there’s no way I can feel safe in ever doing so.
And I’m not at all interested in some “ZFS shim layer” thing either that some people seem to think would isolate the two projects. That adds no value to our side, and given Oracle’s interface copyright suits (see Java), I don’t think it’s any real licensing win either.
Torvalds doesn’t want Linux kernel to get into legal troubles with Oracle in future and hence he refuses to include ZFS in the mainline kernel until Oracle provides a signed letter that a kernel with ZFS will be under GPL license.
And honestly, there is no way I can merge any of the ZFS efforts until I get an official letter from Oracle that is signed by their main legal counsel or preferably by Larry Ellison himself that says that yes, it’s ok to do so and treat the end result as GPL’d.
He is not stopping other (distributions) from using ZFS. But they are on their own.
If somebody adds a kernel module like ZFS, they are on their own. I can’t maintain it, and I can not be bound by other peoples kernel changes.
Canonical, Ubuntu’s parent company, has been too keen on ZFS. Their legal department thinks that including ZFS in the kernel doesn’t make it a derivative work. So they took their chances and now they provide an option to use ZFS on root from Ubuntu 19.10.
Torvalds is also not impressed with ZFS in general
While some people drool over ZFS, Linus Torvalds is not that impressed with ZFS. He doesn’t think it’s using ZFS is a good idea specially when it is not actively maintained by Oracle (after they open sourced it)
The benchmarks I’ve seen do not make ZFS look all that great. And as far as I can tell, it has no real maintenance behind it either any more, so from a long-term stability standpoint, why would you ever want to use it in the first place?
I am no legal expert but if there is even a slightest doubt, I would prefer staying away from ZFS. What do you think of the whole ZFS debate?
So he doesn’t trust Oracle (ZFS) but he does trust Oracle (BTRFS)…
Because of GNU licence of BTRFS. He says that he care about keeping linux GNU licence. Once ZFS would be confirmed as changing its licence, Linus would be ok the integrate it like btrfs, no matter what he said about benchmark ;)
No, it’s not just that. The article quotes “it was always more of a buzzword than anything else”… and “The benchmarks I’ve seen do not make ZFS look all that great. And as far as I can tell, it has no real maintenance behind it either[…]” So no matter the license, he thinks there is no benefit in supporting ZFS in general.
And openZFS is maintained actively. You can check that on openzfs.org and zfsonlinux.org respectively on github.com. Maybe Mr. Torvalds refers to the ZFS at the state when Sun was incorporated?!
There’s certainly a reason why the license is incompatible. Sun is completely wiped out, so how reasonable could it be to trust Oracle?
And aren’t features removed (deduplicated send) due to lacking ressources or capabilities? So lack of maintenance is certainly an issue.
Indeed, there’s more to the statement as one would wish.