Comment by btilly
6 years ago
Here are his reasons for generally avoiding ZFS from what I consider most important to least.
- The kernel team may break it at any time, and won't care if they do.
- It doesn't seem to be well-maintained.
- Performance is not that great compared to the alternatives.
- Using it opens you up to the threat of lawsuits from Oracle. Given history, this is a real threat. (This is one that should be high for Linus but not for me - there is no conceivable reason that Oracle would want to threaten me with a lawsuit.)
I'm baffled by such arguments.
> It doesn't seem to be well-maintained.
The last commit is from 3 hours ago: https://github.com/zfsonlinux/zfs/commits/master. They have dozens of commits per month. The last minor release, 0.8, brought significant improvements (my favorite: FS-level encryption).
Or maybe this is referred to the 5.0 kernel (initial) incompatibility? That wasn't the ZFS dev team's fault.
> Performance is not that great compared to the alternatives.
There are no (stable) alternatives. BTRFS certainly not, as it's "under heavy development"¹ (since... forever).
> The kernel team may break it at any time, and won't care if they do.
That's true, however, the amount is breakage is no different from any other out-of-tree module, and it unlikely to happen with a patch version of a working kernel (in fact, it happen with the 5.0 release).
> Using it opens you up to the threat of lawsuits from Oracle. Given history, this is a real threat. (This is one that should be high for Linus but not for me - there is no conceivable reason that Oracle would want to threaten me with a lawsuit.)
"Using" it won't open to lawsuits; ZFS has a CDDL license, which is a free and open-source software license.
The problem is (taking Ubuntu as representative) shipping the compiled module along with the kernel, which is an entirely different matter.
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[¹] https://btrfs.wiki.kernel.org/index.php/Main_Page#Stability_...
> ZFS has a CDDL license
Java is GPLv2+CPE. That didn't stop Oracle because, as Linus pointed out in the email, Oracle regards their APIs as a separate entity to their code.
Googles Java implementation wasn't GPL licensed, so neither its implementation nor its interface could have been covered by the OpenJDK being GPLv2. I think RMS wouldn't sit by idly either if someone took GCC and forked it under the Apache license.
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> There are no (stable) alternatives. BTRFS certainly not, as it's "under heavy development"¹ (since... forever).
Note that they don't mean "it's unstable," just "there are significant improvements between versions." Most importantly:
> The filesystem disk format is stable; this means it is not expected to change unless there are very strong reasons to do so. If there is a format change, filesystems which implement the previous disk format will continue to be mountable and usable by newer kernels.
...and only _new features_ are expected to stabilise:
> As with all software, newly added features may need a few releases to stabilize.
So overall, at least as far as their own claims go, this is not "heavy development" as in "don't use."
Some features such as Raid5 were still firmly in "don't use if you value your data" territory last I looked. So it is important to be informed as to what can be used and what might be more dangerous with btrfs
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There's differing opinions of BTRFS's suitability in production - it's the default filesystem of SUSE on one hand, on the other RedHat has deprecated BTRFS support because they see it as not being production ready and they don't see it being production ready in the near future. They also feel that the more legacy linux filesystems have added features to compete.
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bcachefs should be heavily supported, it doesn't get nearly enough for what it supposes to do: https://www.patreon.com/bcachefs
I've been looking forward to using bcachefs as I had a few bad experiences with btrfs.
Is bcachefs more-or-less ready for some use cases now? Does it still support caching layers like bcache did?
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Many of the advanced features aren't implemented yet though, like compression, encryption, snapshots, RAID5/6....
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Honestly just use ZFS. We've wasted enough effort over obscure licensing minutia.
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> There are no (stable) alternatives. BTRFS certainly not, as it's "under heavy development"¹ (since... forever).
Unless you are living in 2012 on a RHEL/CENTOS 6/7 machine, btrfs has been stable for way too long. I have been using btrfs as the sole filesystem on my laptop in standard mode, on my desktop as RAID0 and my NAS as RAID1 for more that two years. I have experienced absolutely zero data loss. Infact, btrfs recovered my laptop and desktop from broken package updates many times.
You might have had some issues when you tried btrfs on distros like RHEL that did not backport the patches to their stable versions because they don't support btrfs commercially. Try something like openSUSE that backports btrfs patches to stable versions or use something like arch.
> That's true, however, the amount is breakage is no different from any other out-of-tree module, and it unlikely to happen with a patch version of a working kernel (in fact, it happen with the 5.0 release).
This is a filesystem that we are talking. In no circumstances will any self respecting sysadmin use a file system that has even a small change of breaking with a system update.
I also used btrfs not too long ago in RAID1. I had a disk failure and voila, the array would be read-only from now on and I would have to recreate it from scratch and copy data over. I even utilized the different data recovery methods (at some point the array would not be mountable no matter what) and in the end that resulted in around 5% of the data being corrupt. I won't rule out my own stupidity in the recovery steps, but after this and the two other times when my RAID1 array went read-only _again_ I just can't trust btrfs for anything other than single device DUP mode operation.
Meanwhile ZFS has survived disk failures, removing 2 disks from an 8 disk RAIDZ3 array and then putting them back, random SATA interface connection issues that were resolved by reseating the HDD, and will probably survive anything else that I throw at it.
I believe he's referring to the raid 5/6 issues
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A former employer was threatened by Oracle because some downloads for the (only free for noncommercial use) VirtualBox Extension Pack came from an IP block owned by the organization. Home users are probably safe, but Oracle's harassment engine has incredible reach.
My employer straight up banned the use of VirtualBox entirely _just in case_. They'd rather pay for VMWare Fusion licenses than deal with any potential crap from Oracle.
Anecdotal, but VirtualBox has always been a bit flaky for me.
VMWare Fusion, on the other hand, powers the desktop environment I've used as a daily work machine for the last 6 months, and I've had absolutely zero problems other than trackpad scrolling getting emulated as mouse wheel events (making pixel-perfect scroll impossible).
Despite that one annoyance, it's definitely worth paying for if you're using it for any serious or professional purpose.
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This is throwing the baby along with the bathwater.
VirtualBox itself is GPL. There is no lawsuit risk.
What requires "commercial considerations" is the extension pack.
The extension pack is required for:
> USB 2.0 and USB 3.0 devices, VirtualBox RDP, disk encryption, NVMe and PXE boot for Intel cards
If licensing needs to be considered (ie. in a corporate environment), but one doesn't need the functionalities above, then there's no issue.
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Well ... that sounds initially unreasonable, but then if I think about it a bit more I'm not sure how you'd actually enforce a non-commercial use only license without some basic heuristic like "companies are commercial".
Is the expectation here that firms offering software under non-commercial-use-is-free licenses just run it entirely on the honour system? And isn't it true that many firms use unlicensed software, hence the need for audits?
IIRC VirtualBox offers to download the Extension Pack without stating it's not free for commercial use. There isn't even a link to the EULA in the download dialog as far as I can tell (from Google Images, at least). Conversely, VirtualBox itself is free for commercial use. Feels more like a honeypot than license auditing.
They can also apply stronger heuristics, like popping up a dialogue box if the computer is centrally-managed (e.g.: Mac MDM, Windows domain, Windows Pro/Enterprise, etc.).
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They harass universities about it too. Which is ludicrous, because universities often have residence halls, and people who live there often download VirtualBox extensions.
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> There is no conceivable reason that Oracle would want to threaten me with a lawsuit.
I don't think it has to be conceivable with Oracle...
Unfortunately I have to agree with Linus on this one. Messing with Oracle's stuff is dangerous if you can't afford a comparable legal team.
"Oracle's stuff" can most often be described more accurately as "what Oracle considers its stuff".
Linus is distributing the kernel, a very different beast from using a kernel module. I can't imagine Oracle targeting someone for using ZFS on Linux without first establishing that the distribution of ZFS on Linux is illegal.
> there is no conceivable reason that Oracle would want to threaten me with a lawsuit.
Money. Anecdotally that's the primary reason Oracle do anything.
If anyone thinks this is hyperbole :
I worked for a tiny startup (>2 devs full time) where Oracle tried to extract money from us because we used MariaDB on AWS.
If you think this sounds ridiculous you probably got it right.
(Why? Because someone inexperienced with Oracle had filled out the form while downloading the mySQL client.)
Re-reading my comment in daylight I realize I got one detail almost exactly wrong: we were always <= 2 developers, but it seems everyone understood the point anyway - we were tiny, but not too tiny for Oracles licensing department.
Well... Serves you about right for choosing MySQL over PostgreSQL :)
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"there is no conceivable reason that Oracle would want to threaten me with a lawsuit."
Don't be so sure about this.
None of these are good reasons to purposely hinder the optional use of ZFS as a third party module by users, which is what Linux is doing.
Can you expand? I'm no expert - use linux daily but have always just used distro default file system. Linus' reasons for not integrating seems pretty sensible to me. Oracle certainly has form on the litigation front.
Linus' reasons for not integrating ZFS are absolutely valid and it's no doubt that ZFS can never be included in the mainline kernel. There's absolutely no debate there.
However the person he is replying to was not actually asking to have ZFS included in the mainline kernel. As noted above, that could never happen, and I believe that Linus is only bringing it up to deflect from the real issue. What they were actually asking is for Linux to revert a change that was made for no other reason than to hinder the use of ZFS.
Linux includes a system which restricts what APIs are available to each module based on the license of the module. GPL modules get the full set of APIs whereas non-GPL modules get a reduced set. This is done strictly for political reasons and has no known legal basis as far as I'm aware.
Not too long ago a change was made to reduce the visibility of a certain API required by ZFS so only GPL modules could use it. It's not clear why the change was made, but it was certainly not to improve the functionality of the kernel in any way. So the only plausible explanation to me is that it was done just to hinder the use of ZFS with Linux, which has been a hot political issue for some time now.
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This want a case of "purposely hinder", but rather the zfs nodule broke because of some kernel changes. The kernel is careful to never break userspace and never break its own merged modules. But if you're a third-party module then you're on your own. The kernel developers can't be responsible for maintaining compatibility with your stuff.
The changes conveniently accomplished nothing except for breaking ZFS. Furthermore, just because they don't officially support ZFS doesn't mean they must stonewall all the users who desire the improved compatibility. Reverting this small change would not be a declaration that ZFS is officially supported.
> - Performance is not that great compared to the alternatives.
CoW filesystems do trade performance for data safety. Or did you mean there are other _stable/production_ CoW filesystems with better performance? If so, please do point them out!
XFS on LVM thin pool LV. Stable and performant as far as I can tell.
My terrible experiences with thin pools makes me see btrfs as a pool of wonderful, trouble-free and perfect code.
Just ask yourself what happens when a thin pool runs out of actual, physical disk blocks?
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XFS is not copy on write.
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>- Using it opens you up to the threat of lawsuits from Oracle. Given history, this is a real threat. (This is one that should be high for Linus but not for me - there is no conceivable reason that Oracle would want to threaten me with a lawsuit.)
No. Distributing (ie. precompiled distro with ZFS) will. You are free to run any software on your machine as you so desire.
This reminds me of the adaptation of a Churchill quote that "ZFS is the worst of the file systems, except for all others."