ZFS for Linux

Bralkein · 2006-05-03 19:00:17

Although ZFS looks rather interesting, I think you're selling Reiser4 short. When I used it, I had a few problems with it, but it was extremely fast. Part of the problems the kernel devs have with it is that filesystems are supposed to be implemented through VFS, but VFS does not have the APIs to support all of the stuff that Reiser4 can do. Also, Reiser4 seems to be very desktop-oriented, and if you read interviews with Hans Reiser about Reiser4, he seems most excited about all the possibilities that it brings for desktop systems, through e.g. in-built support for metadata. It is true that certain operations, such as mounting, can take quite a long time on some systems. I think this is due to the fact that part of the design philosophy of both Reiser file systems is that disk access is much more of a bottleneck than CPU, so it makes sense to use the available CPU time to reduce disk bandwidth requirements. Also, with mounting, the amount of time taken is not so important, unless you are frequently mounting and dismounting the filesystem - but I don't think many people do this. Most people will mount their root file system exactly once, that time obviously being at boot. I would gladly accept a design decision that means 5 extra seconds are spent mounting my FS at boot, if it grants me an extra 10% disk throughput for disk operations that I frequently use.

Like I said, ZFS certainly looks good, and I would be really glad to see it fully supported in Linux, since this will only make Linux stronger. However, Sun are more in the business of server sales and support, and as such the features that ZFS brings to the table are more server-oriented. I have a server at my Mum's house, and I would be very interested in giving ZFS a try for that, but not on my desktop machine. I would be happier using Reiser4 there, I am just waiting to see if the kernel devs will ever accept it into the mainline kernel (though I use various patches from MM anyway, so maybe I'll just start using that instead.)

Gullible Jones · 2006-05-03 20:22:09

I dunno, the ability to format a directory instead of making a whole new partition is something that *should* be included in any new filesystems. If we can't have ZFS, we ought to at least implement some if its ideas - block checksums come to mind here!

Regarding Reiser4... The mount times are just inexcusable. The reason for ReiserFS mount times has been pointed out, and just leaving it in the completely rewritten version is stupid.

Now, I'll be the first to admit that Hans Reiser is far smarter than I will ever be... But Reiser4 is really not looking incredible. It doesn't support volumes larger than ReiserFS did, it doesn't have extremely significant performance benefits... I suppose the plugins are nice, true, but I'm not sure it's such a great idea to implement them at the filesystem level. I don't think it's really got anything revolutionary going for it.

Also, looking ahead, Linux is really going to need a good filesystem with support for *huge* volumes. I think NILFS might work for that, once it's ready, although I do kind of wonder about fragmentation on log-structured filesystems. There's also UFS2, which IIRC supports maximum volume and file sizes similar to those of ZFS; having full support for that might be nice for those using Linux to handle staggeringly colossal amounts of data, e.g. CERN or Fermilab, though I'm not exactly sure about the various performance aspects of said filesystem.

Bralkein · 2006-05-03 23:46:47

Well I might be getting a 500GB disk soon, which should hopefully let me explore various filesystems. Maybe I could do some benchmarks on it. Would you be interested in that?

Gullible Jones · 2006-05-04 01:31:23

500GB? Forget Reiser4 then, it would probably take over a minute to mount.

Bralkein · 2006-05-04 02:46:26

Well that's what I'm going to find out! Seriously, it would be cool to do some FS benchmarks. If I get this disk in the end, (it depends on how much money I have) then 500GB would be a good amount to play with. Maybe we could get a little team together and come up with some good tests for the various filesystems. Install Solaris to test out ZFS and everything.

Neuro · 2006-05-04 11:45:42

That's a really cool idea. A cross-OS filesystem benchmark

Could you please include benchmarks of UFS under all 4 major BSDs?

Bralkein · 2006-05-04 14:41:20

Haha jeez, that would be a major undertaking... TBH, I'd rather do it all on Linux, but ZFS seems like a really interesting FS to test, and you need Solaris for that. Maybe to test ZFS, it would be a good idea to also test another filesystem on Solaris, e.g. Ext3 (assuming Solaris supports that), so that you would be able to see the difference between Ext3 on Solaris and Ext3 on Linux, and maybe draw some conclusions about what the difference would be if ZFS were run on Linux.

OTOH, I would imagine that the Linux Ext3 driver would be much better optimised than a Solaris Ext3 driver, so perhaps that's a bad idea. Maybe it would be better to hold off any comparisons 'til Linux gets a stable ZFS driver... but that seems like it might be quite a while! Oh woe!

Gullible Jones · 2006-05-04 17:13:45

From the looks of it it seems that Linux will never be able to get a ZFS driver legally.

whargoul · 2006-05-04 19:35:41

Gullible Jones wrote:

From the looks of it it seems that Linux will never be able to get a ZFS driver legally.

Sad... It sounds really nice though.

Gullible Jones · 2006-05-04 19:59:22

Well, that's why I'm saying we ought to have a filesystem that implements at least some of those features...

Bralkein · 2006-05-04 22:54:47

Why not legally?

iphitus · 2006-05-04 22:55:29

Gullible Jones wrote:

From the looks of it it seems that Linux will never be able to get a ZFS driver legally.

No, Linux could quite easily get a legal copy of the filesystem.

The issue is that the CDDL code of the filesystem as used in Solaris, cannot be included with the GPL'ed kernel, without relicensing it. It's up to Sun to do that.

So for the filesystem to be merged into vanilla, it would require an complete rewrite from scratch, using no CDDL licensed code, or a relicensing/dual licensing from Sun

Alternatively, it would also legal for it to be distributed seperately, such as in the form of a patch like reiser4.

James

IANAL, but this is what my weak understanding of licensing and my reading of LKML tells me.

Bralkein · 2006-05-04 22:58:55

Yeah, right, that's what I thought... and if ZFS is really that great, surely there will be some demand to get it put into the kernel by Red Hat, Novell et al, even if it requires writing from scratch.

Moo-Crumpus · 2006-05-05 14:54:27

Sometimes, I am really tired of those licence debates, and feel like "just gimme that thing, stupid". I know, I know, on the long run this would be the end of linux ... and most of the days I am really convinced of GPL. But (loop)

Gullible Jones · 2006-05-05 20:01:47

On the one hand, the GPL's parasitic nature is what keeps the BSDs from using ALSA, and lots of other stupid things... On the other hand it's what's kept Linux alive for so long.

Perhaps the GPL should be revised so that source code taken directly from GPL software could only be used in FOSS projects, but not necessarily GPLed ones? That way, the first generation of derivative software products (ugh, sounds like marketese :oops: ) would have to be OSS, even if they weren't GPL.

Also, how would it work if Linux were relicensed under the LGPL?

(IMHO... ZFS is quite obviously miles ahead of any filesystem Linux supports right now, and frankly, if we don't want it to become obsolete, we'd better try hard as hell to develop ZFS drivers, or to develop a similar filesystem of our own. Also FWIW, I wouldn't be surprised if Sun's licensing was, in part, a deliberate move to make it harder for Linux to support the filesystem.)

jaboua · 2006-05-05 21:55:20

Gullible Jones wrote:

On the one hand, the GPL's parasitic nature is what keeps the BSDs from using ALSA, and lots of other stupid things... On the other hand it's what's kept Linux alive for so long.
Perhaps the GPL should be revised so that source code taken directly from GPL software could only be used in FOSS projects, but not necessarily GPLed ones? That way, the first generation of derivative software products (ugh, sounds like marketese :oops: ) would have to be OSS, even if they weren't GPL.
Also, how would it work if Linux were relicensed under the LGPL?
(IMHO... ZFS is quite obviously miles ahead of any filesystem Linux supports right now, and frankly, if we don't want it to become obsolete, we'd better try hard as hell to develop ZFS drivers, or to develop a similar filesystem of our own. Also FWIW, I wouldn't be surprised if Sun's licensing was, in part, a deliberate move to make it harder for Linux to support the filesystem.)

The only problem with your proposed GPL revision would be that microsoft could relicense all the GNU/Linux components in BSD, and then put it under a proprietary license. That's what the GPL was made to prevent in the first place.

But I wonder, why wouldn't ZFS be legally available in linux? Nvidia drivers for example aren't GPL either, but Linus said it was OK since they weren't written for linux in the first place, but ported afterwords or something - wouldn't that apply for ZFS too?

Gullible Jones · 2006-05-05 22:04:18

Err... I was wrong. :oops:

The problem would be that ZFS's license is not GPL-compatible - it requires improved code to be relayed back to Sun, and since the kernel is all GPL, that would give Sun massive headaches.

It could be a separate patch, as opposed to an implementation in the mainline kernel, but that could cause potential ZFS users tremendous headaches too. Just look at how damn hard it is to get a Reiser4 partition up and running and you'll see what I mean.

Bralkein · 2006-05-06 04:02:46

Yeah, but the thing is, even if the code that Sun have implemented ZFS in is not GPL-compatible, it is still possible to write your own code that implements the ZFS from scratch, wihtout copying a single line of Sun's code.

Gullible Jones · 2006-05-06 10:05:30

Possible, true. Also very damn difficult, I would think.

jaboua · 2006-05-06 12:35:39

Gullible Jones wrote:

Possible, true. Also very damn difficult, I would think.

Agreed... Just look at all the problems they've had making NTFS drivers (and they are still not perfect) - and ZFS has a thousand more features to be implemented than NTFS...

iphitus · 2006-05-06 12:44:38

Although with ZFS there's at least a reference design to work off, no need for reverse engineering.

Bralkein · 2006-05-06 13:40:10

Documents about ZFS can be found [URL=http://www.opensolaris.org/os/community/zfs/docs/]here[/URL]. I'm not a kernel/filesystem guru, but the on-disk specification looks pretty comprehensive to me.

FUBAR · 2006-05-08 14:37:15

Moo-Crumpus wrote:

Seems to be a no:
http://marc.theaimsgroup.com/?l=linux-k … 212352&w=2
Btw, nice ZFS demo:
http://www.opensolaris.org/os/community … os/basics/
http://www.opensolaris.org/os/community … /selfheal/

Even if I only understand half of what's happening, it's friggin' impressive! It makes me want to install OpenSolaris!

user · 2006-05-14 12:40:53

zfs seems good at raid something.
http://unixconsult.org/zfs_vs_lvm.html

Arch Linux

#26 2006-05-03 19:00:17

Re: ZFS for Linux

#27 2006-05-03 20:22:09

Re: ZFS for Linux

#28 2006-05-03 23:46:47

Re: ZFS for Linux

#29 2006-05-04 01:31:23

Re: ZFS for Linux

#30 2006-05-04 02:46:26

Re: ZFS for Linux

#31 2006-05-04 11:45:42

Re: ZFS for Linux

#32 2006-05-04 14:41:20

Re: ZFS for Linux

#33 2006-05-04 17:13:45

Re: ZFS for Linux

#34 2006-05-04 19:35:41

Re: ZFS for Linux

#35 2006-05-04 19:59:22

Re: ZFS for Linux

#36 2006-05-04 22:54:47

Re: ZFS for Linux

#37 2006-05-04 22:55:29

Re: ZFS for Linux

#38 2006-05-04 22:58:55

Re: ZFS for Linux

#39 2006-05-05 14:54:27

Re: ZFS for Linux

#40 2006-05-05 20:01:47

Re: ZFS for Linux

#41 2006-05-05 21:55:20

Re: ZFS for Linux

#42 2006-05-05 22:04:18

Re: ZFS for Linux

#43 2006-05-06 04:02:46

Re: ZFS for Linux

#44 2006-05-06 10:05:30

Re: ZFS for Linux

#45 2006-05-06 12:35:39

Re: ZFS for Linux

#46 2006-05-06 12:44:38

Re: ZFS for Linux

#47 2006-05-06 13:40:10

Re: ZFS for Linux

#48 2006-05-08 14:37:15

Re: ZFS for Linux

#49 2006-05-14 12:40:53

Re: ZFS for Linux

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