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Linus: Don't Use ZFS

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Re: Linus: Don't Use ZFS

#131

Post by spinningslate »

shawnz wrote: post #122
btilly wrote: post #35

Earlier quoted context omitted.

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…

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.

Re: Linus: Don't Use ZFS

#132

Post by pizza234 »

btilly wrote: post #35
Hamuko wrote: post #7

Earlier quoted context omitted.

That's his reasoning for not merging ZFS code, not for generally avoiding ZFS.

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…

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.

---

[¹] https://btrfs.wiki.kernel.org/index.php/Main_Page#Stability_...

Re: Linus: Don't Use ZFS

#134

Post by __jal »

HorstG wrote: post #107
montjoy wrote: post #81

Earlier quoted context omitted.

Last time I used ZFS write performance was terrible compared to an ordinary RAID5. IIRC Writes in a raidz are always limited to a single disk’s performance. The only way to get better write speed is to combine multiple raidzs - which means you need a boatload if disks.

We had a bunch of Thumpers (SunFire X4200) with 48 disks at work, running ZFS on Solaris. It was dog slow and awful, tuning performance was complicated and took ages. One had to use just the right disks in just the right order in RaidZs with striping over them. Swap in a hotspare: things slow to a crawl (i.e. not even Gbit/s). After EoL a colleague installed Linux with dmraid, LVM and xfs on the same hardware: much f…

Sounds like you turned on dedupe, or had an absurdly wide stripe size. You do need to match your array structure to your needs as well as tune ZFS.

On our backup servers (45 disks, 6-wide Z2 stripes) easily handle wire-speed 10G with 32G ARC.

And you're just wrong about snapshots and filesystem counts.

ZFS is no speed demon, but it performs just fine if you set it up correctly and tune it.

Re: Linus: Don't Use ZFS

#135

Post by derefr »

DSMan195276 wrote: post #108
Wowfunhappy wrote: post #87

Earlier quoted context omitted.

But why are all drivers expected to be "part of the project"? We don't treat userspace Linux software that way. We don't consider Windows drivers part of Windows.

It's pretty simple, once they expose such an API they'd have to support it forever, hindering options for refactoring (that happens all the time). With all the drivers in the tree, they can simply update every driver at the same time to whatever new in-kernel API they're rolling out or removing. And being that the majority of drivers would arguably have to be GPL anyway, and thus open-source, the advantages of keepin…

You know, come to think of it, is there anything stopping Linux from having a... FKSE (Filesystem in Kernel SpacE) standard API?

Presumably, such a thing would just be a set of kernel APIs that would parallel the FUSE APIs, but would exist for (DKMS) kernel modules to use, rather than for userland processes to use. Due to the parallel, it would only be the work of a couple hours to port any existing FUSE server over into being such a kernel module.

And, given how much code could be shared with FUSE support, adding support for this wouldn't even require much of a patch.

Seems like an "obvious win", really.

Re: Linus: Don't Use ZFS

#136

Post by StavrosK »

Covzire wrote: post #22
djsumdog wrote: post #11

Earlier quoted context omitted.

Well he had this: > as far as I can tell, it has no real maintenance behind it either any more Which simply isn't true. They just released a new ZFS version with encryption built in (no more ZFS + LUKS) and they removed the SPL dependency (which didn't support Linux 5.0+ anyway). I use ZFS on my Linux machines for my storage and I've been rather happy with it.

Same, for at least 6 years in a 4 drive zraid array. It always reads and writes at full gigabit ethernet speeds and I haven't had any downtime other than maintaining FreeBSD updates which are trivial even when going from 10.x to 11 to 12.

Same here (4-drive raidz for many years), though I do have an issue where deleting large files (~1 GB) takes around a minute and nobody seems to know why (I have plenty free space and RAM)...

Re: Linus: Don't Use ZFS

#137

Post by shawnz »

spinningslate wrote: post #131
shawnz wrote: post #122

Earlier quoted context omitted.

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.

Re: Linus: Don't Use ZFS

#138

Post by zelly »

He's not wrong. ext4 is actually maintained. This matters. ZFS hasn't kept up with SSDs. ZFS partitions are also almost impossible to resize, which is a huge deal in today's world of virtualized hardware.

Honestly Linus's attitude is refreshing. It's a sign that Linux hasn't yet become some stiff design-by-committee thing. One guy ranting still calls the shots. I love it. Protect this man at all costs.

Re: Linus: Don't Use ZFS

#139

Post by timc3 »

HorstG wrote: post #112
voltagex_ wrote: post #44

Earlier quoted context omitted.

Have you got any info on how to do the required tuning that's geared towards a home NAS?

Group your disks in bunches of 4 or 5 per Raidz, no more. And have them on the same controller or SAS-expander per bunch. Use striping over the bunches. Don't use hotspares, for performance maybe avoid RAIDz6. Try out and benchmark a lot. Get more RAM, lots more RAM.

Back when I setup my last ZFS running on OmniOS 5 disks was not optimal, though i am running RAIDZ2

But yes, lots of RAM

Re: Linus: Don't Use ZFS

#140

Post by thu2111 »

organsnyder wrote: post #88
btilly wrote: post #35

Earlier quoted context omitted.

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…

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.

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?

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