LWN.net Logo

Linus on GPLv3 and ZFS

From:  Linus Torvalds <torvalds-AT-linux-foundation.org>
To:  Alexandre Oliva <aoliva-AT-redhat.com>
Subject:  Re: Dual-Licensing Linux Kernel with GPL V2 and GPL V3
Date:  Tue, 12 Jun 2007 08:45:46 -0700 (PDT)
Cc:  Ingo Molnar <mingo-AT-elte.hu>, Tarkan Erimer <tarkan-AT-netone.net.tr>, debian developer <debiandev-AT-gmail.com>, "david-AT-lang.hm" <david-AT-lang.hm>, Linux Kernel Mailing List <linux-kernel-AT-vger.kernel.org>, Andrew Morton <akpm-AT-linux-foundation.org>, Greg KH <greg-AT-kroah.com>
Archive-link:  Article, Thread



On Tue, 12 Jun 2007, Alexandre Oliva wrote:
> 
> Per this reasoning, Sun wouldn't be waiting for GPLv3, and it would
> have already released the OpenSolaris kernel under GPLv2, would it
> not? ;-)

Umm. You are making the fundamental mistake of thinking that Sun is in 
this to actually further some open-source agenda.

Here's a cynical prediction (but backed up by past behaviour of Sun):

 - first off: they may be talking a lot more than they are or ever will
   be doing. How many announcements about Sun and Linux have you seen over
   the years? And how much of that has actually happened?

 - They may like open source, but Linux _has_ hurt them in the 
   marketplace. A lot.

   They almost used to own the chip design market, and it took quite a 
   long time before the big EDA vendors ported to Linux (and x86-64 in 
   particular). But when they did, their chip design market just basically 
   disappeared: sparc performance is so horribly bad (especially on a 
   workstation kind of setup), that to do chip design on them is just 
   idiotic. Which is not to say that there aren't holdouts, but let's face 
   it, for a lot of things, Solaris is simply the wrong choice these days.

   Ergo: they sure as hell don't want to help Linux. Which is fine. 
   Competition is good.

 - So they want to use Linux resources (_especially_ drivers), but they do 
   *not* want to give anything back (especially ZFS, which seems to be one 
   of their very very few bright spots).

 - Ergo: they'll not be releasing ZFS and the other things that people are 
   drooling about in a way that lets Linux use them on an equal footing. I 
   can pretty much guarantee that. They don't like competition on that 
   level. They'd *much* rather take our drivers and _not_ give anythign 
   back, or give back the stuff that doesn't matter (like core Solaris: 
   who are you kidding - Linux code is _better_).

End result:

 - they'll talk about it. They not only drool after our drivers, they 
   drool after all the _people_ who write drivers. They'd love to get 
   kernel developers from Linux, they see that we have a huge amount of 
   really talented people. So they want to talk things up, and the more 
   "open source" they can position themselves, the better.

 - They may release the uninteresting parts under some fine license. See 
   the OpenSolaris stuff - instead of being blinded by the code they _did_ 
   release under an open source license, ask yourself what they did *not* 
   end up releasing. Ask yourself why the open source parts are not ready 
   to bootstrap a competitive system, or why they are released under 
   licenses that Sun can make sure they control.

So the _last_ thing they want to do is to release the interesting stuff 
under GPLv2 (quite frankly, I think the only really interesting thing they 
have is ZFS, and even there, I suspect we'd be better off talking to 
NetApp, and seeing if they are interested in releasing WAFL for Linux).

Yes, they finally released Java under GPLv2, and they should be commended 
for that. But you should also ask yourself why, and why it took so long. 
Maybe it had something to do with the fact that other Java implementations 
started being more and more relevant?

Am I cynical? Yes. Do I expect people to act in their own interests? Hell 
yes! That's how things are _supposed_ to happen. I'm not at all berating 
Sun, what I'm trying to do here is to wake people up who seem to be living 
in some dream-world where Sun wants to help people. 

So to Sun, a GPLv3-only release would actually let them look good, and 
still keep Linux from taking their interesting parts, and would allow them 
to take at least parts of Linux without giving anything back (ahh, the 
joys of license fragmentation). 

Of course, they know that. And yes, maybe ZFS is worthwhile enough that 
I'm willing to go to the effort of trying to relicense the kernel. But 
quite frankly, I can almost guarantee that Sun won't release ZFS under the 
GPLv3 even if they release other parts. Because if they did, they'd lose 
the patent protection.

And yes, I'm cynical, and yes, I hope I'm wrong. And if I'm wrong, I'll 
very happily retract anything cynical I said about Sun. They _have_ done 
great things, and maybe I'm just too pessimistic about all the history 
I've seen of Sun with open source.

The _good_ news is that Jonathan Schwartz actually does seem to have made 
a difference, and I hope to God he is really as serious about 
open-sourcing things as he says he is. And don't get me wrong: I think a 
truly open-source GPLv3 Solaris would be a really really _good_ thing, 
even if it does end up being a one-way street as far as code is concerned!

			Linus


(Log in to post comments)

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 18:14 UTC (Tue) by JoeBuck (subscriber, #2330) [Link]

Yes, I am an EDA developer, who once developed primarily on Solaris/Sparc and who now develops primarily on Linux. Sun dropped the ball years ago; they had a Solaris/x86 in the early 90s that never got any attention, because Sun management wanted to put "all the wood behind SPARC".

Provided that Sun eventually does go the GPLv3 route, or if other GPLv3 code appears interesting, Linux could start a transition to a dual license: GPLv2 or GPLv3. The advantage of those terms is that they would achieve the advantages of GPLv3 (better internationalization, compatibility with other free software licenses such as Apache's) but still avoid the DRM restriction Linus objects to (anything GPLv2 permits would still be allowed). Furthermore the kernel already has a lot of "GPLv2 or any later version" code. A transition would take a while to do, and a complete transition might require replacement of code from authors who won't play or can't be located. But the Mozilla project managed to do it; if Linus asked, I would expect the vast majority of developers to go along.

But it's up to him.

I'm sure Sun is only making these moves to attract developers. But I'm happy to see more choices.

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 18:27 UTC (Tue) by cpeterso (subscriber, #305) [Link]

Furthermore the kernel already has a lot of "GPLv2 or any later version" code.
I thought the kernel code was licensed under GPLv2 only? http://lxr.linux.no/source/COPYING
Also note that the only valid version of the GPL as far as the kernel is concerned is _this_ particular version of the license (ie v2, not v2.2 or v3.x or whatever), unless explicitly otherwise stated.

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 19:54 UTC (Tue) by yokem_55 (subscriber, #10498) [Link]

The kernel as a complete work is GPL V2 only. Many of the individual files in the source though have the V2 or later language in them. So, if a relicensing project were started to bring the complete work of the kernel to GPL V3, those files would already be taken care of.

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 18:27 UTC (Tue) by arcticwolf (guest, #8341) [Link]

How would a dual-licensed Linux help, though? If you go that route, you still can't port things like ZFS, since that'd be - if it's GPL'ed at all - GPLv3 only. So the only way to port it would be to essentially split Linux into a GPLv2 version and a GPLv3 version; and given that there'd likely be code (old or new) that would be GPLv2 only, the latter would not even be a superset of the former.

So as long as Linu(x|s) doesn't go GPLv3, period, there would really be no way to make code flow from Solaris to Linux, and in fact, a dual-licensed version of Linux with an "official", integrated GPLv3 branch would actually make it easier for Sun to pull in code from Linux.

But then, maybe Linus is just a strategic genius, too - maybe all his vocal opposition to the GPLv3 is just a clever ploy to lull Sun into a false sense of security, and once they've released Solaris and/or ZFS under the GPLv3, he'll just switch over as well[1] and reach the rewards. ;)

1. Yeah, I know, he can't just do that, but for the sake of the joke, let's pretend he can.

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 18:52 UTC (Tue) by ajross (subscriber, #4563) [Link]

The v2 and v3 GPL variants are explicitly compatible with each other in both directions. So there's no reason the kernel couldn't simply ship different parts of the tree under different licenses. No fork would be required except in the case where someone wanted to put together a "GPL2 only" distribution for some reason.

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 19:23 UTC (Tue) by dlang (✭ supporter ✭, #313) [Link]

GPLv2 and GPLv3 are not compatible in either direction

the only thing that lets GPLv2 code change to GPLv3 is if people gave the FSF a blank check and said 'GPLv2 or later'

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 21:04 UTC (Tue) by man_ls (subscriber, #15091) [Link]

True:
When we say that GPLv2 and GPLv3 are incompatible, it means there is no legal way to combine code under GPLv2 with code under GPLv3 in a single program. This is because both GPLv2 and GPLv3 are copyleft licenses: each of them says, “If you include code under this license in a larger program, the larger program must be under this license too.” There is no way to make them compatible.

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 8:20 UTC (Wed) by forthy (guest, #1525) [Link]

The FSF took great efforts that GPL versions can be made compatible. The paragraph that deals with it is section 9 of the GPL. Read it, especially the last part - many files in the Linux kernel are not explicitely restricted to a specific GPL versions, which means "any version". And section 6 makes sure that everybody receives a license from the original licensor, not from a compilation editor like Linus Torvalds.

The compilation editor (Linus Torvalds) can set terms under which he redistributes the work, i.e. conditions he has to follow. But since everybody receives the license from the original licensors, this "restriction" is null and void, you still can make a compilation yourself which does not restrict the license version, and then, most parts of Linux are compatible with GPLv3 (because you can either choose any GPL or explicitely v2 or later).

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 9:37 UTC (Wed) by man_ls (subscriber, #15091) [Link]

That kind of compatibility is not much help, unless all of the kernel is licensed as "v2 or later". As long as there is a single file licensed under "v2 only", it becomes impossible to link with a single "v3 only" file.

Meanwhile, relicensing all files under a "v2 or later" license might seem to be a necessary first step to a GPLv3 kernel. But given Linus' reluctance to blanket license, I would rather expect a "dual v2-v3" license, if the migration is to be done at all.

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 13:09 UTC (Wed) by job (subscriber, #670) [Link]

Maaaybe there was a good reason why the FSF recommended the use of "v2 or later" licensing. Then you basically leave the choice to the user. I never understood what Linus didn't like about that, except some unspecified fear of the FSF, which would be not only ridicolous but also unfortunate.

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 13:36 UTC (Wed) by man_ls (subscriber, #15091) [Link]

It is not so unreasonable: Linus said:
How can you _ever_ sign anything sight unseen? That's just stupid, and that's totally regardless of any worries about the FSF.
Said that way, it looks like the correct thing to do. However, given that (as you say) "v2 or later" licensing gives the choice to the user, I'm not particularly worried about misuse.

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 21:56 UTC (Wed) by notamisfit (guest, #40886) [Link]

It creates the possibility that code created in a downstream work may not be usable upstream. Linus has put his cards on the table in the past; he wants code back.

Linus on GPLv3 and ZFS

Posted Jun 14, 2007 1:59 UTC (Thu) by error27 (subscriber, #8346) [Link]

Instead of "ridiculous and unfortunate" I would say "justified by current events."

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 19:06 UTC (Tue) by proski (subscriber, #104) [Link]

We could also theorize that Linus is hinting at the possibility of switching Linux to GPLv3 to dissuade Sun from releasing ZFS under GPLv3.

But why would not Linus want ZFS in the kernel? The history of Linux shows that reimplemented code is more successful that ported code. XFS and JFS are rarely used, whereas ext2 and ext3 are wildly popular.

Patent issues: GPLv3 and ZFS

Posted Jun 12, 2007 19:30 UTC (Tue) by dwheeler (guest, #1216) [Link]

Patent issues. If Sun releases ZFS under GPLv3, ZFS is patented, and its patents on ZFS are valid, then anyone else using GPLv3 can use ZFS. They can even "bring in" the GPLv3 code and completely rewrite it, so the IMPLEMENTATION may be different but they'd still be okay legally (I think). Using GPLv2 wouldn't give them access to patents released only under GPLv3.

Patent issues: GPLv3 and ZFS

Posted Jun 12, 2007 20:01 UTC (Tue) by atai (subscriber, #10977) [Link]

One would expect Sun already considered this aspect already assuming Sun will release OpenSolaris under the GPL v3.

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 1:48 UTC (Wed) by wolfrider (guest, #3105) [Link]

> JFS [is] rarely used

--Depends on who you ask. I use JFS now almost exclusively for Vmware and "bkps" (read: large) filesystems, where before I would use ReiserfsV3 with notail.

--After seeing how fast (and reliable) JFS is, I switched almost all my Reiser filesystems over to it - and have been much happier. Reiser is great for root and squid (tail-packing) but not ideal when you're trying to run a VM from a USB2 IDE drive. JFS makes it usable.

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 20:43 UTC (Tue) by JoeBuck (subscriber, #2330) [Link]

If all of the kernel code were GPLv2 || GPLv3, it could be combined with a GPLv3 ZFS. The collection as a whole would be GPLv3 only if ZFS were added, but ZFS could be a module, and everything would be legal, while embedded software developers who want to do DRM could still use the rest of Linux (except ZFS).

Linus on GPLv3 and ZFS

Posted Jun 12, 2007 22:28 UTC (Tue) by cyperpunks (subscriber, #39406) [Link]

Linus is right, Sun don't want Linux source code, they want Linux' kernel hackers (and
then later Linux' users).

Of course CDDL is hopeless is this regard as hackers must transfer copyright to Sun, who
want to do that?

Sun have to fix the bootstrap problem too: it's now not possible to build a complete
free Solaris "distribution". You must use some non free Sun tools at some point.

Who wants to contribute to project you can't build yourself?

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 0:00 UTC (Wed) by JoeBuck (subscriber, #2330) [Link]

To be fair, Sun's launching a project, called "Indiana", to correct that deficiency and produce something that would resemble a GNU/Linux distribution. It will take them some time to do it, but I'm looking forward to it.

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 12:36 UTC (Wed) by paulj (subscriber, #341) [Link]

Of course CDDL is hopeless is this regard as hackers must transfer copyright to Sun, who want to do that?

This is false.

You need to sign a contributors agreement with Sun, granting Sun joint ownership, if you wish to have Sun incorporate any contribution to various open-source projects which Sun founded and maintain (such as OpenSolaris, amongst other projects).

However the CDDL does not require any copyright transfership, and you're quite free to take and hack away on CDDLed code, like OpenSolaris, without giving copyright ownership to Sun or anyone else.

for the clueless

Posted Jun 12, 2007 20:01 UTC (Tue) by ccyoung (guest, #16340) [Link]

such as myself,

what is ZFS and what makes it so hot?

Google is your friend

Posted Jun 12, 2007 20:21 UTC (Tue) by rfunk (subscriber, #4054) [Link]

http://www.opensolaris.org/os/community/zfs/

for the clueless

Posted Jun 12, 2007 21:14 UTC (Tue) by huerlisi (guest, #44534) [Link]

Because it's a nice product of computer engineering. Here's a quote from a nice-to-read geeky background article :
64 bits would have been plenty ... but then you can't talk out of your ass about boiling oceans then, can you?
Simon

WAFL != ZFS

Posted Jun 12, 2007 21:56 UTC (Tue) by qu1j0t3 (guest, #25786) [Link]

I have to assume Linus knows that. Sigh. If not, like another poster here, he should Google... I'm tired of posting ZFS linkfests ;-)

He's treading close to the FUD-line with this one. There's also a hidden assumption here that Jonathan Schwartz is being disingenuous with his massively revamped corporate strategy.

Sun's a hardware company. They're happy for you to run Linux on your Sun gear if you prefer - it's a supported option - heck, they even support Windows.

WAFL != ZFS

Posted Jun 12, 2007 23:03 UTC (Tue) by allesfresser (subscriber, #216) [Link]

I don't think it's anywhere near FUD, personally. It sounded simply like classic Linus--he's being very transparently honest. He hopes and wishes that Schwartz and company are being as open and forthright as they claim to be, but knowing human nature and the temptations that beset us, he is keeping his powder dry and his head down, so to speak.

forthright != Linus

Posted Jun 12, 2007 23:43 UTC (Tue) by qu1j0t3 (guest, #25786) [Link]

It's not very "forthright" to inject snide Linusisms such as "the only really interesting thing they have is ZFS, and even there, I suspect we'd be better off talking to NetApp"! XFS is already integrated, and that has about as much in common with ZFS as WAFL does.

It comes across as sour grapes about the license, and even some N-I-H ("core Solaris: who are you kidding - Linux code is _better_"). Btw, there is as much spurious rancor of the opposite polarity from the Sun camp, as recent zfs-discuss flamefests can attest.

Why can't we all just get along? - Admit that some people like BSD license, some people like GPL, Sun likes CDDL for now, and ZFS plain rocks... :)

Linux devs ignore it at their peril; Linus, being an engineer of Sun's calibre, could do a much more helpful job of deconstructing the issue.

forthright != Linus

Posted Jun 13, 2007 0:03 UTC (Wed) by JoeBuck (subscriber, #2330) [Link]

The issue with Sun is not that they prefer a particular license, but that they are choosing to license patents only to code that uses their particular license, while IBM, Red Hat, Novell, and others are licensing a number of patents (or in Red Hat's case, all their patents) to developers who use a much larger set of open source licenses.

okay but,

Posted Jun 13, 2007 0:21 UTC (Wed) by qu1j0t3 (guest, #25786) [Link]

This still does not fully explain to me why, to date, kernel devs aren't looking dispassionately as the affordances of ZFS and how they might have them without stepping on anyone's patent*. Max V. Yudin recently asked on zfs-discuss,

... is it legal to write ZFS clone from scratch while maintaining binary compatibility with original?

Jeff mentioned in his blog that Sun filled 56 patents on ZFS related technologies. Can anybody from the company provide me with more information about this?

If porting ZFS to Linux kernel is not an option and I were to implement different file system with ZFS ideas in mind how can I be safe and not break any Sun patents?

There has been no meaningful resolution of his questions. At least it may prove that, thanks to software patents, interesting development is now impossible. So much for stimulating innovation...

* - I suppose NetApp has patents too, but perhaps Linus wishes to imply that they would be more tractable to deal with than Sun (maybe he actually knows somebody @ NetApp). Let's dream for a moment, and imagine that Linus and Jonathan, over a piña colada one Sunday, work out a magical way to free ZFS for kernel inclusion. That would be a P/R coup for Sun an order of magnitude greater than even the Apple buzz. Since Solaris 10 famously runs on all varieties of hardware (IBM, HP, Dell, even Macs), I don't seriously think Jonathan believes this would damage hardware sales. Then again, I only have the ponytail, not an MBA, and my bonuses are a few zeroes short of his. ;-)

okay but,

Posted Jun 13, 2007 7:57 UTC (Wed) by TRS-80 (subscriber, #1804) [Link]

One could always start from Sun's GPLv2 ZFS code in GRUB. And Jonathon Schwartz has just posted saying Linux ZFS would have full patent indemnity.

okay but,

Posted Jun 13, 2007 9:38 UTC (Wed) by michaeljt (subscriber, #39183) [Link]

That said "GPL v2 or later" if I read correctly. I didn't take the time to read the code, but presumably that is only code for reading and would not affect potential patents on writing parts.

On another note, if Sun make Solaris GPL3 and accept external contributions, it might get tricky to keep parts (i.e. ZFS) under another licence.

okay but,

Posted Jun 13, 2007 19:51 UTC (Wed) by dlang (✭ supporter ✭, #313) [Link]

note that the zfs code released for grub is not enough to actually be able to write to the filesystem, just enough for grub to be able to find the files that it needs.

Netapp and patents

Posted Jun 22, 2007 7:10 UTC (Fri) by anton (subscriber, #25547) [Link]

I suppose NetApp has patents too, but perhaps Linus wishes to imply that they would be more tractable to deal with than Sun
Yes, Netapp has patents, and they caused Daniel Phillips to stop working on the tux2 filesystem; I have not followed the story enough to know if Netapp did anything other than file the patents to achieve this result.

Netapp's WAFL is not very interesting for Linux anyway, because it requires special NVRAM hardware to buffer writes during some of the more time-consuming operations (e.g., snapshot creation). I don't think that this hardware dependence can be eliminated without major changes to the WAFL code.

Concerning not breaking Sun patents, you can look for older sources where similar ideas have been described, e.g., various papers on log-structured file systems, e.g., our Freenix 2000 paper, or (maybe too young) my file system ideas.

ZFS and WAFL

Posted Jun 15, 2007 0:02 UTC (Fri) by joern (subscriber, #22392) [Link]

> XFS is already integrated, and that has about as much in common with ZFS as WAFL does.

That is plain wrong. XFS is in the huge class of traditional filesystems with a static mapping between file offsets and device offsets. ZFS is in the somewhat smaller (ignoring reseach projects) class of COW filesystems, just like WAFL. Anyone unable to see the similarities is well advised to read more and write less. ;)

ZFS and WAFL

Posted Jun 17, 2007 15:30 UTC (Sun) by qu1j0t3 (guest, #25786) [Link]

As you see I haven't studied XFS in depth, but I was under the impression it was COW like ZFS. AFAIK, WAFL also lacks the more interesting features of ZFS (foremost being end-to-end checksumming).

ZFS and WAFL

Posted Jun 17, 2007 17:29 UTC (Sun) by joern (subscriber, #22392) [Link]

Checksums are easy to add once you have a COW format. Either you add them to the block pointers, as ZFS did, or you add them to the objects themselves, as JFFS2 and LogFS did.

Either way you have an incompatible format change. But the amount of code affected if rather small. Took about 1-2% of the effort to design a new filesystem in the LogFS case.

btrfs?

Posted Jun 17, 2007 18:06 UTC (Sun) by qu1j0t3 (guest, #25786) [Link]

Maybe so, but there's quite a lot of catch-up to do. Once you have COW, transactions, and checksums, then you want self-healing; then snapshots; pools; quotas; compression; and so on, until you eventually have something like ZFS. :)

Linus' grandstanding aside, it's possible there is quiet work going on to improve the situation, as David Magda commented on zfs-discuss:

Somewhat off topic, but it seems that someone released a COW file system for Linux (currently in 'alpha'):

	* Extent based file storage (2^64 max file size)
	* Space efficient packing of small files
	* Space efficient indexed directories
	* Dynamic inode allocation
	* Writable snapshots
	* Subvolumes (separate internal filesystem roots)
	- Object level mirroring and striping
	* Checksums on data and metadata (multiple algorithms available)
	- Strong integration with device mapper for multiple device support
	- Online filesystem check
	* Very fast offline filesystem check
	- Efficient incremental backup and FS mirroring

	http://lkml.org/lkml/2007/6/12/242
	http://oss.oracle.com/~mason/btrfs/

Via Storage Mojo

	

btrfs?

Posted Jun 17, 2007 19:05 UTC (Sun) by joern (subscriber, #22392) [Link]

> Maybe so, but there's quite a lot of catch-up to do. Once you have COW, transactions, and checksums, then you want self-healing; then snapshots; pools; quotas; compression; and so on, until you eventually have something like ZFS. :)

Sure, ZFS has an impressive set of features. If nothing else, it has showed how things can be done. And I have little doubt that btrfs, which you quoted, will end up having most of those features relatively soon. And even if Chris dies tomorrow, I'll keep working on LogFS.

The only question is when, not if. :)

good to hear

Posted Jun 17, 2007 19:15 UTC (Sun) by qu1j0t3 (guest, #25786) [Link]

The only question is when, not if. :)

From comments I've heard, and the buzz around Linus' and Jon's posts, there seems to be considerable community interest around ZFS (I don't want to use anything else, or wait, so I switched to Solaris 10 some time ago).

Look forward to more news on this front. Did you follow-up on LKML? (I have not checked :)

good to hear

Posted Jun 17, 2007 21:43 UTC (Sun) by joern (subscriber, #22392) [Link]

> From comments I've heard, and the buzz around Linus' and Jon's posts, there seems to be considerable community interest around ZFS (I don't want to use anything else, or wait, so I switched to Solaris 10 some time ago).

> Look forward to more news on this front. Did you follow-up on LKML? (I have not checked :)

My personal interest is in flash, not hard disks. Therefore ZFS is impressive technology, but solving someone else's problem. It is not the last word in filesystems either, as the fsck will run for hours or days if it ever becomes necessary. So there remain valid reasons to work on different filesystems.

Impressive technology none the less.

COW for Flash?

Posted Jun 18, 2007 17:26 UTC (Mon) by qu1j0t3 (guest, #25786) [Link]

It has been said that COW is ideal for Flash. Can you explain why ZFS isn't relevant here?

There is no fsck; ZFS is "always consistent on disk" (through COW+atomic transactions). It seems to me this is a necessary invariant to achieve its other features (such as snapshots). Debate flares up (occasionally) as to whether a scavenger will be necessary. If so, it won't much resemble 'fsck' - and certainly won't be run in normal operation or after reset/powerfail/etc (ZFS behaviour under impromptu reset is extremely well tested).

I suspect, but correct me if I'm wrong, once you "know" you've lost data in ZFS (through exhausting redundancy or ditto blocks), it's actually gone by definition, and unrecoverable by re-creating links. No doubt Bonwick et all have explained it better somewhere...

COW for Flash?

Posted Jun 19, 2007 8:17 UTC (Tue) by joern (subscriber, #22392) [Link]

> It has been said that COW is ideal for Flash. Can you explain why ZFS isn't relevant here?

Raw flash behaves sufficiently different to hard disks that some ZFS design assumptions become untrue. Flash has large erase blocks. Within erase blocks, data must be written from front to back. Writing the block again requires erasing all of it. So the filesystem block size either has to be equal to the erase block size, or you need garbage collection. And with garbage collection comes a nasty deadlock problem most people don't even realize exists. :)

Next comes wear out and protection against it. Afaics, ZFS has several hot zones that receive significantly more writes than others.

I guess those two are the big reasons.

linux core better?

Posted Jun 12, 2007 23:54 UTC (Tue) by genius (guest, #19981) [Link]

i dont think i can agree with it. that was a blog last time about the linux kernel having problem scaling beyond 8-way compared to bsd. not sure whether they have solved it. on the other hand, linux has definitely revived interest in unix.

linux core better?

Posted Jun 13, 2007 0:11 UTC (Wed) by JoeBuck (subscriber, #2330) [Link]

You are seriously out of date; folks at SGI have Linux running on 1024 processors.

The Solaris and BSD folks cannot claim to be more scalable than Linux at this point; it appears that the reverse is true.

what epoch are you posting from?

Posted Jun 13, 2007 2:37 UTC (Wed) by xoddam (subscriber, #2322) [Link]

> linux kernel having problem scaling beyond 8-way compared to bsd.

You're several years behind. A long time_t in LKML-land.

what epoch are you posting from?

Posted Jun 13, 2007 3:03 UTC (Wed) by Nick (subscriber, #15060) [Link]

Poster is probably talking about this blog entry

http://jeffr-tech.livejournal.com/5705.html

So he is right, and Linux did have a problem on this
workload. Basically it was a combination of a glibc
inefficiency and the fact that nobody seems to have
reported such a workload before. The fix was basically
a small change to the way malloc/free works, and a
little patch to the kernel to optimise the new path
used by glibc.

http://www.thisishull.net/showpost.php?s=5d2bfa8b5a070728...

That post found the fixes to have eliminated the big
dropoff. Note it still doesn't scale past 8-way, but
this is likely to be a MySQL issue -- BSD doesn't do
any better.

what epoch are you posting from?

Posted Jun 14, 2007 7:36 UTC (Thu) by drag (guest, #31333) [Link]

Those things seem to have triggered some sort of bug.

Rest assured people do have real-world Linux boxes that have over 512 cpus in a single system image. SGI has boxes, at least, have Linux boxes with 4096 cpus in a single system image.

As far as clustering goes.. there are Linux systems with tens of thousands of cpus going.

Linux kernel itself does scale past 8 cpus. Of course nothing is perfect.

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 10:03 UTC (Wed) by venkatesh045 (guest, #45744) [Link]

You could read Jonathan Schwartz's reply to this post. I think he clarifies a lot of issues as to what Sun is looking at. This post is actually worth a good read.

Linus on GPLv3 and ZFS

Posted Jun 13, 2007 12:25 UTC (Wed) by marduk (subscriber, #3831) [Link]

Reads like typical salesmanship. Sales talk always "sounds" good...

I actually disagreed with his implication that communities don't compete (only corporations). There exists competition in the OSS community.

competition

Posted Jun 13, 2007 12:47 UTC (Wed) by qu1j0t3 (guest, #25786) [Link]

There difference may be that it's augmentative competition rather than destructive - In business, it's optimal to completely eliminate rivals. In open source, you don't have to do that; you can just do better. It's a more pure meritocracy. I hope. :)

That said, there's still some dirty pool played from time to time, but since it's played in the open, it hardly festers.

Copyright © 2007, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds