Big News for ZFS on Linux

http://dtrace.org/blogs/ahl/2016/03/07/big-news-for-zfs-on-linux/

by bcantrill • 10 years ago

222 138 10 years ago

Hug of Death on the site as of 1250 CST

This was in the news before. What's the big new thing about this article? It reads like a writeup of the news of yesterday. Also, ZFS is not coming to Linux as such, it's coming to Ubuntu specifically and the article does not clear up the detail why this is now possible for Ubuntu but was not possible for the rest of the Linux community.

andreaso• 10 years ago

I'd imagine there are people who consider the article relevant based on its author.

https://en.wikipedia.org/wiki/Adam_Leventhal_%28programmer%2...

dyladan• 10 years ago

AFAIK they are saying that because it is a DKMS module and Linux is not a derivative work, they are not restricted from using it by the license. By Canonical's interpretation, it would only become an issue if they were to build the support directly into the kernel natively rather than using a standalone zfs.ko file.

Keep in mind IANAL and this is just my limited understanding of the issue.

jerf2• 10 years ago

Am I really reading this correctly, that the plan seems to be "ignore the possible license incompatibility and hope Oracle doesn't sue?"

Because of all ways to fill in the "Hope _____ doesn't sue" plan, "Oracle" must be in the top 5 worst companies to fill in the blank with in the tech industry.

adamleventhal5• 10 years ago

Agreed on the second point, but no one (to my knowledge) is contending that Oracle's copyrights or patents are being violated.

Grishnakh• 10 years ago

I'm not a lawyer or an expert on the CDDL, however it could be that the license incompatibility is one-way: maybe only the GPL rightsholders have reason to sue.

Sanddancer• 10 years ago

No, the plan was, "have the lawyers evaluate the possible license incompatibility, decide that the really isn't one, and release the module." The SFLC is essentially running a FUD campaign here by trying to paint Canonical as being reckless.

derefr• 10 years ago

One nice thing about things "coming to Ubuntu specifically" is that a lot of people get used to what Linux is "like" through Ubuntu. So when Ubuntu does something, people start looking for that thing whenever they use Linux generally. It generates demand, which pushes changes through.

dsp12345• 10 years ago

ZFS is not coming to Linux as such, it's coming to Ubuntu specifically

This is a faulty understanding of the issue. Other distros such as Debian are packaing 'ZFS on Linux'. Ubuntu is not the first one to offer the ability to have ZFS on Linux in the distros main repository. The difference is actually that the other distros distribute the ZFS code as source, then have the user compile it on their own computer, and then those distros consider that end product as non-redistributable. Whereas Ubunutu is doing the compilation on their own, then distributing the resulting binary work. That's the actual difference.

ryao7• 10 years ago

Sabayon Linux has been shipping binary modules for years. No one has ever complained.

adamleventhal5• 10 years ago

It's a fair critique though I didn't write this because I thought I was breaking news. The Canonical announcement was honestly exciting for me, in particular because they evaluated the licensing issues and decided that they were within their rights to provide ZFS to their users. It seemed though that the voices of practitioners was being drowned out by those focusing exclusively on legal matters. I was hoping to provide some information for those unacquainted with both the technology and the legal miasma. Regardless, I'm excited that ZFS is about to have many more users.

jinxedID• 10 years ago

Google cache: http://webcache.googleusercontent.com/search?q=cache:scs1wYb...

NoGravitas• 10 years ago

I suspect "Just ignore the licences and focus on the technology" is not going to fly with enterprise customers.

VonGuard• 10 years ago

Totally correct. However, it may fly just fine with Ubuntu's "just install a damn Linux and get the app online" crowd. Ubuntu makes Linux easy to install and maintain, and that could be enough for some users. They only need one or two giant apps to grow here in order for it to be called a success.

jra_samba3• 10 years ago

Yep. It's all fun and games until the lawsuits start :-).

I don't understand people like this. If they were advocating using pirate copies of Microsoft Windows or other proprietary software, would they be saying "ignore Microsoft legal department and focus on how cool it is that I get a free copy of Windows ?

Stupid, stupid, stupid.

adamleventhal5• 10 years ago

Lots of people do exactly that. In fact, many companies even use software for which the licenses have lapsed or they never owned licenses in the first place. Sometimes it's by accident; in other cases it's a knowing acceptance of risk.

kbenson• 10 years ago

I don't think that's a relevant comparison at all. What we have here is two open source technologies that have traditionally been kept from being used together because of specific clauses in their licenses, and some lawyers who have looked at it and are vouching that it's not a problem. That's far from ignoring the proprietary closed source, for-profit licensing of a product where it's very clear cut. The lawyers may be wrong, and it's probably a good idea for enterprise customers to steer clear, but the whole point is that there is some valid contention over whether the technologies can be used together. There is not valid contention over whether you can use Windows without a license.

brazzledazzle2• 10 years ago

I think it's safe to say there's a world of difference between license violations for a piece of software that's closed source, proprietary and sold for profit and a license incompatibility on two open source projects caused by a single clause in licenses that are otherwise compatible.

You may have the chops and cred to call someone stupid that wrote dtrace but I'd certainly hesitate before doing so myself.

adamleventhal5• 10 years ago

"As with anything, evaluate the technology, evaluate the risks, and move on."

I've been selling to enterprise customers for a little while now. All technology has risk, new technology and the status quo alike. Companies weigh those risks against the expected benefits. Some folks will obviously avoid the brouhaha completely; it makes sense. Others will decide that the benefits outweigh the risk; there's nothing less comprehensible about that decision.

_ph_• 10 years ago

No, the licenses are not ignored. Both, the GPL and the CDDL require the source available for any copy of the resulting program distributed. In that spirit, there is no license violation. There is some disagreement to which extend linking programs under those licenses is technically possible. But the verdict is still out, whether this is a problem at all. But for the goals both licenses aim for - open source which stay open source, is not violated. This is not a company shipping a closed source executable based on modified sources. They are just shipping precompiled binaries based on available sources.

yarrel• 10 years ago

The comments agree -

http://dtrace.org/blogs/ahl/2016/03/07/big-news-for-zfs-on-l...

gtirloni2• 10 years ago

What's the situation on btrfs? It was supposed to make ZFS not that big deal anymore on Linux.

JoshTriplett• 10 years ago

It would if done, but it's not quite there yet.

joshbaptiste• 10 years ago

Depends on which mailing list you read, the usual consensus I see is it's kinda production ready, though openSUSE has switched to Btrfs as its main file system.

cyphar• 10 years ago

[Disclaimer: I work for SUSE]

SUSE Linux Enterprise also uses btrfs by default. There's also a bunch of features like booting into snapshots and snapper (snapshots taken before zypper transactions and on regular intervals with decaying granularity) which are in both OpenSUSE and SLE.

tristanz2• 10 years ago

I can confirm that btrfs has major problems with tons of snapshots. The entire system will hang for minutes on random intervals and go completely unresponsive for hours when using admin commands. The many snapshots use case is pretty common when dealing with containers, even it everything works fine for simple setups.

cmurf7• 10 years ago

How many is tons? I've not had such problems with hundreds of snapshots. There are reports on the btrfs list with problems involving many thousands. I have no idea how ZFS snapshots perform when there are hundreds to thousands.

The other thing that matters a ton is kernel version, the development is so heavy there are thousands of insertions+deletions per kernel cycle that even in a year it's ordinary to consider those kernels "old" on the list. Most distros by default use old kernels by Btrfs development standards. The exception is Fedora, and openSUSE who do lots of backports explicitly to support Btrfs.

nisa• 10 years ago

There are lot of missing parts. Everything beyond using it for single disks or with RAID1 is still experimental. It's slow for a lot of use cases like VMs or OLTP ( http://blog.pgaddict.com/posts/friends-dont-let-friends-use-...) and using nodatacow does not count!

RAID1 is implemented to use the oddness of the pid to decide which disk to read from... RAID5/6 have huge performance problems in certain use-cases. Write hole is apparently still a thing.

Quota seems to be still broken or difficult to handle, the tooling is not exactly nice or intuitive (this may change in the future).

Hardware failure handling is nonexistent - it can't detect a broken drive.

Lot's of other gotchas. Just read the mailing list. I've been fighting against btrfs for a while and I'm happy when I'm not having to deal with it. Works probably fine for desktop usage but don't bother stressing it - at the moment it will break horrible.

cmurf7• 10 years ago

Lots of gotchas yes, but it's about as rare to see data loss on Btrfs as it is on say linux-raid@ list for mdadm or LVM and those are much more mature. More often is the case of some suboptimal behavior and the recommendation to get the data off the volume and onto a newly created one. Very inconvenient for some users to be sure, but also not data loss. About the worst I've seen lately that wasn't hardware related needed data scraped using btrfs restore (the tool the extracts data from an unmountable filesystem).

cmurf7• 10 years ago

Single, raid 0, 1, 10 are stable on stable hardware. Where ZFS is definitely more mature is parity raid. If you need parity raid and a snapshotting Cow filesystem and you're not a tester, then you'd want to pick ZFS. But Btrfs is ~ 6 years behind ZFS maturity wise? Maybe in some sense longer because ZFS had a more aggressive start?

There are definitely things Btrfs can already do that ZFS cannot, like read-writable snapshots, no parent-child dependency (you can create a snapshot and immediately delete the original), growing pools is easier/faster without having to build new arrays or sequentially replace devices and resilver, etc. And just in the last week there's an experimental encryption patch for per subvolume encryption (eventually per file similar to f2fs and ext4), so the situation is heavy development.

cmurf7• 10 years ago

An often missed feature is the seed device. Any Btrfs volume can be flagged as a read-only seed. Mount it, you can add a 2nd device, and now re-mount. It's a union filesystem like thing. Changes only go to the 2nd device. If you used 'btrfs remove" on the 1st device, data is migrated to the 2nd device and the 1st is removed, so it replicates the filesystem. The seed setting can be applied to multiple device volumes. So you can add this 2nd device, make that volume a read-only seen, and add a 3rd device for read-write, and so on.

bladerunner822• 10 years ago

ZFS on Linux. No, thank you. I'll continue to use ZFS natively under FreeBSD, which is arguably a far better OS for what ZFS users would be wanting anyway. Been using *BSD since the late 90s. Never a real issue short of HW failure. I cannot say the same for the painful times I was forced to use Linux.

ZFS is indeed a lifesaver, but we in the BSD camps have know this for many moons.

matthewmacleod• 10 years ago

This is a relatively useless contribution to the discussion. Given that there are obviously reasons why Linux has been successful while BSDs have seen less popular usage, it must be the case that Linux or its ecosystem offers features not found elsewhere.

Adding ZFS to Ubuntu is a benefit to everybody, and a smug, holier-than-thou attitude really does nothing to further the conversation about the technology.

jra_samba3• 10 years ago

Nope. Adding a legally licensed copy of ZFS to Ubuntu is a benefit to everybody. Oracle haven't seen fit to do that, and they're the only ones who can.

Sticking a hack-licensing-job into Ubuntu is damaging to the Linux ecosystem, certainly not a benefit.

mioelnir3• 10 years ago

I do not think it is a benefit to everybody. In fact, I think it will tarnish ZFS as a technology.

ZOL still has some very clunky usability integrations (zpool status vs spare, sudo requirements, device name instabilities etc). I'm running ZOL on production servers, and sometimes it feels like back in the day when I tried to get the first ZFS patchsets against FreeBSD7 to run on my P3 with 1.5GB RAM. Sometimes worse.

The majority of Ubuntu users will not attribute these deficiencies to the ZOL port, but to "ZFS". We will see a lot of "So $XYZ has ZFS, well, I have tried it on Ubuntu and it s".

acdha2• 10 years ago

Do you commonly find content-free insults to be an effective form of advocacy? I've used (Free|Open)BSD over the same time period and can point to specific areas which were better (e.g. NFS client stability) or worse (e.g. package management, video drivers) compared to Linux, and both would need to be mentioned in the context of specific versions. If you want to do anything more than make people dislike BSD fanboys, try stating something specific and be prepared to back your assertions up with evidence.

bladerunner822• 10 years ago

Not a fanboy, thank you, just a happy IT pro. We use and prefer BSD and attendant software because we prefer the BSD/CDDL(ZFS)/MIT and similar licenses. The GPL is off-putting for what we do, so we avoid using Linux or other GPL'd software where equivalent BSD (or similar)-licensed software is extant.

skrowl• 10 years ago

Can I have big news on ZFS (or BTRFS) for Windows now? I've heard how awesome this filesystem is, but I still can't use it.

michaelmrose• 10 years ago

Seems unlikely that either will ever come to windows guess you should check out ReFS or install Linux

https://en.m.wikipedia.org/wiki/ReFS#/search

ryao7• 10 years ago

The O3X project lead has joked about porting ZFS to Windows after he finished the Mac OS X port. That is the only discussion of porting it to Windows thus far, although there was one guy who tried reimplementing it as a userspace filesystem on Windows, but that did not get far.

ThatPlayer• 10 years ago

https://github.com/maharmstone/btrfs

This guy is writing a windows driver for Btrfs

wpietri• 10 years ago

My favorite quote from the piece: "And it is the height of delusion to think that Oracle would grow ears to hear, a heart to care, and a brain to decide." And this is coming from a former Oracle employee.

asendra• 10 years ago

Now, how 'bout them Apples err Macs?

srgpqt• 10 years ago

https://openzfsonosx.org/

jordigh3• 10 years ago

I know it seem silly to care about licensing in this case, since it's about GPL incompatibility between two free licenses. However, the problem here is the precedent that it sets. If ZFS distributed this way, in binary form linked to Linux, does not infringe Linux's copyleft, then this could open the doors for other kinds of proprietary blobs to grow on top of Linux. That is SFC's analysis,

    Indeed, Conservancy believes this situation is one
    battle in a larger proxy war by those who seek to
    limit the scope of strong copyleft generally.

https://sfconservancy.org/blog/2016/feb/25/zfs-and-linux/

I also fear about what Oracle could do, as they are copyright holders of parts of Linux (btrfs) and might decide to make things difficult for Canonical. Oracle has misused copyleft aggressively in the past, trying to strong-arm people into buying GPL exceptions for MySQL when they didn't need one, although in this case, they probably do have a good case for why a GPL exception would be necessary.

dbcurtis3• 10 years ago

So, correct me if I'm wrong, but isn't the license incompatibility related to shipping binaries of zfs? If a user chooses to compile locally from zfs sources, then the license issues don't apply, correct? So this is not an issue for, say, Gentoo, Funtoo, LFS, etc, and only an issue for Canonical because they are not interested in a mechanism that allows users to build packages from source, am I correct? I'm thinking something something along the lines of "Here is a tarball containing the sources and a container instance you can spin up. It leaves a .deb behind." What part of this am I missing?

semi-extrinsic• 10 years ago

On ArchLinux, a user (big shout-out to demizer) maintains a set of ZFS packages on AUR that basically do this (build from Git). On Arch, installing ZFS is a one-liner, e.g.

   $ yaourt -S zfs-git

Here is the source for the build script for the zfs-git package:

https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=zfs-g...

danudey• 10 years ago

Two points to this:

First, it's not without precedent. qmail's license prohibited binary redistribution (as well as modified source code distribution), and Debian's solution was packages that, as part of the install, patched, built, and installed qmail from sources on the target machine.

Secondly, this is already an option. The ZFS on Linux project [0] provides packages which do exactly this, by:

1. Distributing kernel sources and building them against the currently install(ed) kernel(s) via dkms. This is actually a common mechanism for module distribution, and is also used by Virtualbox, or anyone else distributing kernel extensions, closed-source or not, which aren't included in the mainline kernel.

2. Providing the userspace binaries to interact with the custom-built ZFS kernel modules built on behalf of the user in #1.

The difference here is Ubuntu distributing binary versions of the modules in the base install, which is important for things like installing on ZFS root, or accessing ZFS filesystems during install.

rcthompson2• 10 years ago

Yes, the only incompatibility arises upon distribution of binary files compiled from both ZFS sources and Linux sources. As of version 15.10, Ubuntu already provides for downloading and compiling the ZFS sources using dkms[1]. However, binary distribution is unquestionably more convenient. Source distribution requires installation of a compiler, which may not be desirable in all environments. For example, in a Live CD linux installer, where space is at a premium, enabling installation onto a ZFS filesystem would require the ZFS sources, the appropriate Linux headers, and a compiler to build the ZFS kernel module all to be included on the disc, instead of just the binary module.

[1] http://packages.ubuntu.com/search?keywords=zfs-dkms

ryao7• 10 years ago

Gentoo ships ZFS kernel binaries via the LiveDVD. There are plenty of Gentoo derivatives that ship kernel binaries binaries too. It is not shipped on the minimal install media yet because I have not yet marked it stable in the tree because of the /dev/ZFS ABI being unstable. I am in the process of rectifying this. I have already put what should be the future stable ABI into the tree. Users found a few issues with it, so I need to resolve them. Once they are fully resolved and I am certain no more linger, I will mark it as stable and the modules should make their way onto the minimal install media like they had on the LiveDVD.

bcantrill• 10 years ago

So you're implying that Oracle would use its standing as a Linux copyright holder to sue Canonical for violating the GPL by integrating the (Oracle copyrighted!) CDDL'd ZFS? On the one hand, I give points for the absurdity of the scenario -- and that it makes no sense would certainly not dissuade Oracle. But on the other hand, even this bizarre scenario is missing something that all of these litigation scenarios seem to lack: damages. James Bottomley explored this issue[1], and I continue to be amazed that others either ignore it or don't treat it explicitly, as it will be the first question that will be asked by any lawyer: where are the damages? I actually ask this earnestly: can those who fear litigation here at least take a swing at establishing the economic harm here?

[1] http://blog.hansenpartnership.com/are-gplv2-and-cddl-incompa...

adamleventhal5• 10 years ago

https://www.softwarefreedom.org/resources/2016/linux-kernel-...

"Nominal statutory damages, divided among the thousands of copyright holders entitled to equal shares, scarcely lift the matter above the level of damnum absque injuria."

foobarqux• 10 years ago

zanny• 10 years ago

I also fear about what Oracle could do, as they are copyright holders of parts of Linux

They have already published commits to Linux under the GPL, they cannot just "take it back". The worst Oracle does is stop contributing to the kernel, which they rarely do to begin with. The "worst" Oracle can do is sue third parties that violate the GPL on their part of the kernel - which would predominantly be proprietary vendors.

pilif2• 10 years ago

They are also the copyright holder of a huge chunk of ZFS' code. So they can also sue Canonical over their violation of the CDDL which oracle (as the copyright holder) has licensed ZFS under.

the_mitsuhiko• 10 years ago

then this could open the doors for other kinds of proprietary blobs to grow on top of Linux.

Isn't that good?

vacri• 10 years ago

then this could open the doors for other kinds of proprietary blobs to grow on top of Linux.

But it's not a binary blob - the source code is supplied with the binary.

IshKebab• 10 years ago

The door is already open - nVidia's graphics driver is closed source.

Besides it should be possible to easily distribute third party binary drivers for Linux and have some reasonable expectation that they work. The fact that you can't is one of the biggest reasons Android updates suck so much.

jordigh3• 10 years ago

The door is already open - nVidia's graphics driver is closed source.

The situation with the nvidia driver relies on the part of the API that the Linux devs have claimed is not GPL. When nvidia wants more API, the Linux devs have pushed back against that:

http://linux.slashdot.org/story/12/10/11/1918251/alan-cox-to...

I don't know how this compares to ZFS. But regardless, there's another thing at play here, the method of distribution. Nvidia doesn't ship Linux together with its blob. I think that if nvidia did that, we would have a situation more analogous to ZFS + Ubuntu.

qb45• 10 years ago

NVIDIA doesn't actually release precompiled modules, only OS-agnostic blob and Linux-specific source which you are free to build yourself.

However, there are other, valid examples like Linksys routers shipping with binary drivers for Broadcom NICs.

sarath7492• 10 years ago

Real useful

sarath7492• 10 years ago

zsf?

DCKing2• 10 years ago

Last I joined in on the discussion I got quite convinced by the argument "if Nvidia can use a propietary license for their Linux graphics driver, then Canonical can use the CDDL for their ZFS driver". Substitute for any other propietary modules that people like to load in their Linux kernels.

Can anyone point me out why this argument is wrong? Googling around for this I was actually suprised that propietary kernel modules are in fact a debated topic (obviously to little success of the opponents), but doesn't the practical existence of propietary kernel modules at least show that no-one has had a problem with this for a long time, legally speaking?

mschwaig2• 10 years ago

The problem is not the use per se, the problem is delivering them to the user as one blob of software together. This is not a problem with proprietary graphics drivers, since you can just download them after setting up you system. However, if you want to boot from a ZFS disk, you need the ZFS driver and the only way to obtain it at that point is effectively from the installation medium.

DCKing2• 10 years ago

OK, fair enough. So distributions that ship the Nvidia drivers in their distro install image (AFAICT OpenELEC does this, not Canonical though) should be in trouble then? And Canonical would find a way around this by autodownloading the ZFS driver when the user select the "ZFS" option in the installer?

fweespeech• 10 years ago

This isn't quite correct.

Nothing really prevents the LiveUSB distribution from writing to itself under ext3, build the ZFS during installation, then use the binary compiled from this process to set it up on the actual SSDs/HDDs. This is legally essentially the same binary blob Nvidia driver as you aren't distributing the binary.

I'm assuming the reason this wasn't done was due to the convenience + you'd need to setup the USB like:

https://help.ubuntu.com/community/LiveCD/Persistence

But once you compiled it on the persistent partition, you'd be able to perform the installation just fine legally and technically is my understanding.

dTal• 10 years ago

Surely that ship sailed on Android a long time ago? Proprietary drivers, shipped to the user with Linux as a single blob, is the norm. It's the biggest problem facing Linux today, much bigger than no ZFS - it kills the concept of a "distro" on the biggest class of personal computers. How does this not violate the GPL?

jordigh3• 10 years ago

nvidia is using parts of the Linux API that the Linux developers have explicitly declared to not activate copyleft. They have at times asked for more non-GPL APIs, which I think has been denied:

http://linux.slashdot.org/story/12/10/11/1918251/alan-cox-to...

I don't know what the situation is with ZFS with regards to the APIs that it's using.

There is also the question of how the software is being combined and distributed. If you receive ZFS and Linux as a "single work", which in SFC's view Ubuntu is doing by putting it all together in a neat little binary package, then the copyleft might activate.

iam-TJ3• 10 years ago

If I may I'd like to share my understanding of the technical aspects which, I feel, makes the issue easier to comprehend.

It also pays to be precise and lack thereof is why so many people are confused and conflicted about the licensing.

The Canonical Kernel Team has added the 'OpenZFS on Linux' source-code [0] in the ./zfs/ directory of the Ubuntu 4.4+ kernel tree [1].

The ZFS modules are built using the OpenZFS on Linux project's stand-alone build tools.

As I understand it from reading the code and following some ZFS project developer discussions the OpenZFS on Linux code is partitioned into common parts that are largely unchanged on all the operating systems it is ported to, plus (in this case) a Linux-specific glue layer that translates the Solaris API to the Linux API in the Solaris Porting Layer (SPL). Each part is built as separate modules; there are 8:

  /lib/modules/${VERSION}/kernel/zfs/avl/zavl.ko
  /lib/modules/${VERSION}/kernel/zfs/nvpair/znvpair.ko
  /lib/modules/${VERSION}/kernel/zfs/spl/spl.ko
  /lib/modules/${VERSION}/kernel/zfs/splat/splat.ko
  /lib/modules/${VERSION}/kernel/zfs/unicode/zunicode.ko
  /lib/modules/${VERSION}/kernel/zfs/zcommon/zcommon.ko
  /lib/modules/${VERSION}/kernel/zfs/zfs/zfs.ko
  /lib/modules/${VERSION}/kernel/zfs/zpios/zpios.ko

The licenses of each module:

  $ find . -type f | while read F; do echo "${F} $( modinfo -F license ${F})"; done | sort
  ./avl/zavl.ko CDDL
  ./nvpair/znvpair.ko CDDL
  ./splat/splat.ko GPL
  ./spl/spl.ko GPL
  ./unicode/zunicode.ko CDDL
  ./zcommon/zcommon.ko CDDL
  ./zfs/zfs.ko CDDL
  ./zpios/zpios.ko GPL

These binary kernel objects (a.k.a. modules) are distributed in the Ubuntu linux-image-${VERSION}_${ARCH}.deb [2] according to Canonical's interpretation as an aggregate work as far as copyright is concerned. That is, works from different projects in the same container, as in e.g. an ISO image.

As can be seen above the 'glue' layer (SPL) is under the GPL. 'zfs.ko' depends on 'spl.ko' (needs to dynamically link to it at run-time):

  $ modinfo -F depends zfs/zfs.ko 
  spl,znvpair,zunicode,zcommon,zavl

The modules under the CDDL contain the core OpenZFS code which is not derived in any way from Linux.

This suggests to me that any conflict between the CDDL and GPLv2 occurs in the OpenZFS on Linux port/project itself, not between the Linux kernel project GPLv2 license and the OpenZFS on Linux CDDL.

In other words, if there is a violation of the GPLv2 as Software Freedom Conservatory (SFC) claim, it occurs in the distribution of the OpenZFS on Linux binaries themselves, since that will combine both CDDL and GPLv2 binaries, even if that was distributed as a stand-alone package (e.g. OpenZFSonLinux.deb) - regardless of whether those binary modules are aggregated with the Linux kernel or not.

I'm pointing this out since most commentary I've read seems to assume that when "GPLv2" is mentioned it means the Linux kernel licence, whereas this analysis suggests the conflict is in the OpenZFS on Linux project's use of CDDL and GPLv2 if distributed in binary form.

There may be an additional viewpoint: that the code in 'spl.ko' (The Solaris Porting Layer) is a derivative of the Linux kernel code; I'm not clear if that is the case or if it would have any impact on the SFC 'binary distribution' theory.

Moving on... once installed on a target system there is a kernel image, Linux mainline dynamically loadable kernel modules, and third-party kernel modules (ZFS, DKMS-based modules, etc.):

  /boot/vmlinuz-${VERSION}
  /lib/modules/${VERSION}/kernel/
  /lib/modules/${VERSION}/kernel/zfs/
  /lib/modules/${VERSION}/updates/

Assuming ZFS is in use as the root file-system the ZFS modules will be copied into the initial ramdisk by the 'update-initramfs' tool scripts:

  /boot/initrd.img-${VERSION}

At boot-time the kernel will dynamically load the ZFS modules from this initial RAM disk image; This is the point where dynamic linkage actually occurs.

This is also usually the focus of arguments about GPLv2 compatibility, as in, for example, the nvidia kernel module.

In the nvidia case, rather like OpenZFS on Linux, the core code is not derived from Linux but is stand-alone and common across other operating systems (Windows, BSD). An nvidia GPLv2 API translation module is dynamically built (using DKMS) to match the kernel installed/running version(s) on the target system to the nvidia 'common core' binary blob library.

The obvious difference (setting aside the nvidia vs OpenZFS licenses) is OpenZFS on Linux API translation (SPL) is pre-built and distributed as a binary by Canonical/Ubuntu.

[0] https://github.com/zfsonlinux/ [1] http://kernel.ubuntu.com/git/ubuntu/ubuntu-xenial.git/tree/z... [2] http://packages.ubuntu.com/xenial/amd64/linux-image-4.4.0-10...

nkurz4• 10 years ago

I think everything you say is correct. I presume you've read it, but Eben Moglen and Mishi Choudhary give a fairly clear summary of the legal issues here: https://www.softwarefreedom.org/resources/2016/linux-kernel-...

The problem is solely with distributing in "object code or executable form" a "work" based on a GPLv2 program without also providing the source to that work under a GPLv2 license: http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html

Practically everyone agrees that if the end user puts the GPL and CDDL pieces together (whether compiled from source or downloaded as separate binaries) that there is no legal problem. The issue is whether the conjoined pieces that Ubuntu plans to distribute constitute a single "work", for if so the GPL says that this "work" cannot be distributed with the ZFS source offered under the less restrictive CDDL.

If Ubuntu's distribution is a single "work", there isn't that much dispute that it would be considered a derivative work of the constituent pieces. So the question becomes, does a compiled kernel plus an assortment of compiled kernel modules bundled together in whatever form Ubuntu offers constitute a "work based on the Program" as defined by the GPL license?

Unfortunately, I don't think there is any clear answer possible. The technical logic of the matter is only relevant in so far as one side's lawyer can persuade one or several non-technical judges that their side has more factors in favor of their interpretation than the other side has in its. If it actually went to trial, the outcome (and possible appeals) would be a crap-shoot.

ericfrederich• 10 years ago

on by default != default filesystem right?

fibo• 10 years ago

I hope this fixes the "read only filesystem" issue.

shmerl• 10 years ago

And here I was hoping (somewhat) that big news by now would be Oracle relicensing OpenZSF under GPL :))

nailer2• 10 years ago

Canonical had their lawyers review the licenses and deemed their use of Linux and OpenZFS to be in compliance.

So Canonical, a tiny desktop-focused Linux company, have discovered something that Red Hat's well paid lawyers have missed?

rwmj• 10 years ago

Red Hat have $billions more to lose.

ryao7• 10 years ago

Do you have a legal statement from Redhat's lawyers? So far, all I heard about their opinions has been hearsay from third parties.

nailer2• 10 years ago

The proof is in the pudding: no major company has ever shipped zfs on Linux in the last decade, nor will they in the next decade.

git-pull• 10 years ago

Oracle holds a copyright on most of OpenZFS since it was forked from the original ZFS code base. It would be within their rights to decide to relicense ZFS under the GPL.

Why imply it should convert to GPL? It could become GPL compatible by making the license more permissive.

https://blogs.oracle.com/chandan/entry/copyrights_licenses_a...

"A common misconception is about CDDL and GPL incompatibility. (Incompatibility in the sense: to combine two source files, one under GPL and another under CDDL, to create a common executable.) GPL is incompatible with most licenses like Mozilla Public License, Apache, and CDDL. GPL wants you erase those licenses and use GPL in that place, where as these licenses do not permit erasing them. Hence the incompatibility deadlock."

gcb0• 10 years ago

irrelevant politics, but if you aim to be included in the kernel at some point, you must go for GPL or live with "kernel tainted" messages.

which i think is great.

mioelnir3• 10 years ago

Which is the core of the argument. ZFS is simply not aimed at being included in the kernel at some point. Linux user's just wish it were so.

SirMaster• 10 years ago

What about Proxmox?

They are a commercial slightly modified Debian distro who have been shipping ZFS with their ISOs and ready to use out of the box, even from the installer wizard for zfs on root installs for around a year now.

Nobody has said anything about them doing this or sued them or tried to stop them.

They are distributing the ZFS on linux binary kernel module pre-instated as Canonical is about to do with Ubuntu.

jethro_tell• 10 years ago

Who?

Edit: Oracle seems to have very little reason to do anything for precedent. Canonical is both competition and a largish business, that would be done for the money, suing proxmox would look like being a bully.

mankash666• 10 years ago

Why ZFS on Linux when FreeBSD ships with ZFS by default, without any legal quagmires? Also, we need a real open-source, non-GPL competitor to Linux if there's any hope of not being taken hostage by overzealous GPL enforcement by SFC and other GPL right-wingers.

carapace• 10 years ago

"Ignore pedants who would deride your pragmatic use of technology as heretical or immoral."

That sounds like bad advice.

newman314• 10 years ago

"Lawyerly cosplay" ROFLMAO

Zardoz842• 10 years ago

And there is an appreciable performance difference between using ZFS and BtrFS ?

DominoTree• 10 years ago

Massive under certain use cases, and major reliability and feature differences too. A lot of BtrFS is still "in progress" like the copy-on-write stuff and fault detection.

Zardoz842• 10 years ago

Actually I'm using BtrFS on a few Ubuntu server 14.04 virtual machines. It's very nice when I need to add extra hard disk space, and I only need to add or expand de the virtual hard disk, and indicate to the filesystem to append the extra new space. Also, transparent compression comes very useful, on special when our applications are very dependent on I/O performance and need to store a lot of write single time/read a lot of times data.

Big News for ZFS on Linux

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