5 ms·

Another ZFS Port on Linux

70 points by suprasam 7y ago

Skunkleton 7y ago
I hope the port is more stable than their server. Anyone have a mirror?
- mappu 7y ago
  https://web.archive.org/web/20190418224604/https://www.crossmeta.io/another-zfs-port-on-linux/ https://web.archive.org/web/20190418224604/https://www.cross...
oofabz 7y ago
unifying ARC with the OS block cache is huge for performance, i hope this feature is adopted by other ZFS implementations
- lemoncucumber 7y ago
  Apple’s aborted port had this, but it was the source of a lot of bugs and instability. Probably could have been made stable with enough time and effort though.
- drewg123 7y ago
  The lack of a zero-copy sendfile for ZFS is one of several reasons that we (Netflix Open Connect) use UFS on our CDN nodes. It would be interesting to see how he solved this. From a brief look at the FreeBSD code several years ago, I seem to recall that ARC dealt in 8K chunks (maybe because it is the sparc page size??), but x86_64 uses a 4K page size, and mmap() and sendfile() expect to deal in pages. The other issue would be "taming" the ARC. We make heavy use of FreeBSD's SF_NOCACHE flag to sendfile(). This allows us to teach the VM system to keep hot content in the page cache, and drop less popular content.
  - NovaX 7y ago
    > The other issue would be "taming" the ARC Has anyone considered replacing ARC? It actually has fairly poor hit rates compared to other policies, with very modest improvements over LRU. I also wonder how much ghost entries contribute to space overhead, which is actually trivial to remove (ARC is an adaptive SLRU - so replace ghosts with a sampling hill climber).
suprasam 7y ago
Demo regarding unified ARC & Pagecache https://youtu.be/be0ph4b9vUE https://youtu.be/be0ph4b9vUE
- BlackLotus89 7y ago
  Is that video a late april fools joke. I didn't yet watch it fully, but a presentation on zfs on Windows in an Internet Explorer window? Wtf?
  - rincebrain 7y ago
    You know, you say that, but... https://github.com/openzfsonwindows/ZFSin https://github.com/openzfsonwindows/ZFSin (I am aware this is not the codebase the presentation is running on or about.)
    - BlackLotus89 7y ago
      Didn't know that anyway. Thanks for the link
m0zg 7y ago
> with the hope that Oracle may change and again open source their latest ZFS Yeah, bud, good luck with that. Someone hasn't worked with Oracle.
- deleted 7y ago
  [deleted]
rincebrain 7y ago
Not especially compelling as a link when the source repo is still empty, so we only have a video to go by.
patrickg_zill 7y ago
I am certainly looking forward to trying it out! ZFS is a great filesystem and being able to possibly have a better implementation than we do at the moment, or at least, be able to spur additional development and optimization, is very welcome!
gigatexal 7y ago
Needs a repo and build/install instructions. Eager to see how this improves over ZFSonLinux
vbezhenar 7y ago
I hope that more people would help with bcachefs development. It seems like a modern alternative for ZFS with proper license and Linux integration.
- noja 7y ago
  https://bcachefs.org/ https://bcachefs.org/ The name doesn't help. It doesn't sound like a real filesystem (it sounds like something that accelerates a real filesystem)
  - wtallis 7y ago
    Well, it did originate from the realization that a good block caching layer designed for SSDs was most of the way to being a real filesystem in its own right. The caching is the biggest advantage bcachefs has over other filesystems, and the name does end in "FS". Perhaps it's a personal bias that makes you inclined to think dismissively of something as "just" a caching layer, when it's actually a really hard problem?
    - noja 7y ago
      Perhaps it's a personal bias that makes you inclined to think dismissively of something as "just" a caching layer, when it's actually a really hard problem? I was providing a possible answer to the question: why do people not give bcachefs more attention as a filesystem?
    - dijit 7y ago
      > Perhaps it's a personal bias that makes you inclined to think dismissively of something as "just" a caching layer, when it's actually a really hard problem? That’s quite incendiary. I also assumed it was a caching filesystem based on the name. Something you could attach to LVM or BTRFS to cache disk write or read on access. Because despite the fact there is “fs” there is “cache” written there. And caching filesystems would indicate that instead of just using ram it would use some kind of traditional storage. It’s not unthinkable that this is a common thought process. What kind of “personal bias” could exist which alters what a caching filesystem would mean?
jgowdy 7y ago
It's incredible to me how many people are suddenly comfortable violating the license of ZFS, simply because Cannonical says it's okay? This is an open source project, under an OSI approved open source license (CDDL) which is quite known to not be GPL compatible. The license is derived from MPL 1.1, which is also known to not be GPL compatible. Why did they bother creating MPL 2, when we could have just ignored the GPL incompatibility in MPL 1.1? You can't be someone who loses their mind over GPL violations, but then willfully misinterpret someone else's open source license because they have something you want. The developers involved specifically picked CDDL because it wasn't GPL compatible. That was their desire / intent, and so that's the license they went with. By ignoring the license and the clearly known intent of the developers in choosing that license, simply because they made something you really want, I believe that ZFS on Linux is really a form of theft in the open source world. It's the same sort of attitude that leads to GPL violations. I don't agree with making things CDDL to be explicitly GPL incompatible, but I do believe in respecting the author of the software in question and the license he or she chose. If people choose licenses I don't agree with, I don't use their software. I don't just use it anyway and pretend like there's no license issue. You don't have to be RMS to see that these people who are ignoring the licensing issues (not just shipping user mode tools like a FUSE implementation which is legit) honestly don't care about open source and licensing and copyleft. They just see something someone else made that they want and they take it and ignore the licensing and developer intent. How can we hope to enforce the GPL successfully but then ignore other OSI approved licenses when it suits us? This is why big names in Linux kernel development aren't remotely interested in ZFS. Not to mention the fact that the users of ZFS on Linux are all setting themselves up for Oracle to bring the licensing inquisition.
- compsciphd 7y ago
  It's an open legal question if a user loadable module violates the CDDL/GPL. Until its fully litigated, its going to remain an open question. As an example: the FSF's position is that yes, if you dynamically link against a GPLd binary that all the code has to be GPLd, and if one wants to link against a copy-left library in a non copy left program the library has to use the LGPL. However, the LGPL predates dynamic linking. It's from the days of static linking where the (L)GPLd could would be distributed together in a single binary. In the world of dynamic linking that isn't true anymore. A primary example is libreadline. It is (or was?) GPLd and the FSF use this a hammer to try and get other code to be GPL. However, this (as far as I know) was never actually litigated. As another example: the Linux kernel is under GPL2, Linus makes it clear that closed source programs can use the syscall interface without a problem, but its not clear that if he didn't say this that they couldn't. He includes the note to clarify his position that they can for those that would be concerned. i.e. the argument would be that without the syscall note, one couldn't ship any hardware device (say an appliance you stick in your rack) with linux and proprietary software. My gut is that most would find that difficult to swallow. As an aside: I personally feel this has similarity to the google / oracle java lawsuit. If one thinks that APIs cannot be copyrighted then arguably anything that just uses APIs and doesn't embed the actual GPLd code one should be fine as the APIs aren't able to be copyrighted. If on the other hand one views APIs are able to copyrighted as well, then it would be much more clear that the FSF's position is correct. Though the usage might still be fair use (and to an extent one might argue that its even more fair use than Google's usage) If this ever does get litigated, I'll be following closely as would be very interested (intellectually at least) in the result. TLDR: until its actually litigated, everyone who claims to speak an absolute truth is speaking out of their ass. Lawyers are a conservative bunch in general so they'll give you the most conservative answer in terms of what you can do, that doesn't mean its the absolute truth in terms of what you can and cannot do.

70 points by suprasam 7y ago

Skunkleton 7y ago

I hope the port is more stable than their server. Anyone have a mirror?

mappu 7y ago
https://web.archive.org/web/20190418224604/https://www.crossmeta.io/another-zfs-port-on-linux/ https://web.archive.org/web/20190418224604/https://www.cross...

oofabz 7y ago

unifying ARC with the OS block cache is huge for performance, i hope this feature is adopted by other ZFS implementations

lemoncucumber 7y ago
Apple’s aborted port had this, but it was the source of a lot of bugs and instability. Probably could have been made stable with enough time and effort though.
drewg123 7y ago
The lack of a zero-copy sendfile for ZFS is one of several reasons that we (Netflix Open Connect) use UFS on our CDN nodes. It would be interesting to see how he solved this. From a brief look at the FreeBSD code several years ago, I seem to recall that ARC dealt in 8K chunks (maybe because it is the sparc page size??), but x86_64 uses a 4K page size, and mmap() and sendfile() expect to deal in pages. The other issue would be "taming" the ARC. We make heavy use of FreeBSD's SF_NOCACHE flag to sendfile(). This allows us to teach the VM system to keep hot content in the page cache, and drop less popular content.
- NovaX 7y ago
  > The other issue would be "taming" the ARC Has anyone considered replacing ARC? It actually has fairly poor hit rates compared to other policies, with very modest improvements over LRU. I also wonder how much ghost entries contribute to space overhead, which is actually trivial to remove (ARC is an adaptive SLRU - so replace ghosts with a sampling hill climber).

suprasam 7y ago

Demo regarding unified ARC & Pagecache https://youtu.be/be0ph4b9vUE https://youtu.be/be0ph4b9vUE

BlackLotus89 7y ago
Is that video a late april fools joke. I didn't yet watch it fully, but a presentation on zfs on Windows in an Internet Explorer window? Wtf?
- rincebrain 7y ago
  You know, you say that, but... https://github.com/openzfsonwindows/ZFSin https://github.com/openzfsonwindows/ZFSin (I am aware this is not the codebase the presentation is running on or about.)
  - BlackLotus89 7y ago
    Didn't know that anyway. Thanks for the link

m0zg 7y ago

> with the hope that Oracle may change and again open source their latest ZFS Yeah, bud, good luck with that. Someone hasn't worked with Oracle.

deleted 7y ago
[deleted]

rincebrain 7y ago

Not especially compelling as a link when the source repo is still empty, so we only have a video to go by.

patrickg_zill 7y ago

I am certainly looking forward to trying it out! ZFS is a great filesystem and being able to possibly have a better implementation than we do at the moment, or at least, be able to spur additional development and optimization, is very welcome!

gigatexal 7y ago

Needs a repo and build/install instructions. Eager to see how this improves over ZFSonLinux

vbezhenar 7y ago

I hope that more people would help with bcachefs development. It seems like a modern alternative for ZFS with proper license and Linux integration.

noja 7y ago
https://bcachefs.org/ https://bcachefs.org/ The name doesn't help. It doesn't sound like a real filesystem (it sounds like something that accelerates a real filesystem)
- wtallis 7y ago
  Well, it did originate from the realization that a good block caching layer designed for SSDs was most of the way to being a real filesystem in its own right. The caching is the biggest advantage bcachefs has over other filesystems, and the name does end in "FS". Perhaps it's a personal bias that makes you inclined to think dismissively of something as "just" a caching layer, when it's actually a really hard problem?
  - noja 7y ago
    Perhaps it's a personal bias that makes you inclined to think dismissively of something as "just" a caching layer, when it's actually a really hard problem? I was providing a possible answer to the question: why do people not give bcachefs more attention as a filesystem?
  - dijit 7y ago
    > Perhaps it's a personal bias that makes you inclined to think dismissively of something as "just" a caching layer, when it's actually a really hard problem? That’s quite incendiary. I also assumed it was a caching filesystem based on the name. Something you could attach to LVM or BTRFS to cache disk write or read on access. Because despite the fact there is “fs” there is “cache” written there. And caching filesystems would indicate that instead of just using ram it would use some kind of traditional storage. It’s not unthinkable that this is a common thought process. What kind of “personal bias” could exist which alters what a caching filesystem would mean?

jgowdy 7y ago

It's incredible to me how many people are suddenly comfortable violating the license of ZFS, simply because Cannonical says it's okay? This is an open source project, under an OSI approved open source license (CDDL) which is quite known to not be GPL compatible. The license is derived from MPL 1.1, which is also known to not be GPL compatible. Why did they bother creating MPL 2, when we could have just ignored the GPL incompatibility in MPL 1.1? You can't be someone who loses their mind over GPL violations, but then willfully misinterpret someone else's open source license because they have something you want. The developers involved specifically picked CDDL because it wasn't GPL compatible. That was their desire / intent, and so that's the license they went with. By ignoring the license and the clearly known intent of the developers in choosing that license, simply because they made something you really want, I believe that ZFS on Linux is really a form of theft in the open source world. It's the same sort of attitude that leads to GPL violations. I don't agree with making things CDDL to be explicitly GPL incompatible, but I do believe in respecting the author of the software in question and the license he or she chose. If people choose licenses I don't agree with, I don't use their software. I don't just use it anyway and pretend like there's no license issue. You don't have to be RMS to see that these people who are ignoring the licensing issues (not just shipping user mode tools like a FUSE implementation which is legit) honestly don't care about open source and licensing and copyleft. They just see something someone else made that they want and they take it and ignore the licensing and developer intent. How can we hope to enforce the GPL successfully but then ignore other OSI approved licenses when it suits us? This is why big names in Linux kernel development aren't remotely interested in ZFS. Not to mention the fact that the users of ZFS on Linux are all setting themselves up for Oracle to bring the licensing inquisition.

compsciphd 7y ago
It's an open legal question if a user loadable module violates the CDDL/GPL. Until its fully litigated, its going to remain an open question. As an example: the FSF's position is that yes, if you dynamically link against a GPLd binary that all the code has to be GPLd, and if one wants to link against a copy-left library in a non copy left program the library has to use the LGPL. However, the LGPL predates dynamic linking. It's from the days of static linking where the (L)GPLd could would be distributed together in a single binary. In the world of dynamic linking that isn't true anymore. A primary example is libreadline. It is (or was?) GPLd and the FSF use this a hammer to try and get other code to be GPL. However, this (as far as I know) was never actually litigated. As another example: the Linux kernel is under GPL2, Linus makes it clear that closed source programs can use the syscall interface without a problem, but its not clear that if he didn't say this that they couldn't. He includes the note to clarify his position that they can for those that would be concerned. i.e. the argument would be that without the syscall note, one couldn't ship any hardware device (say an appliance you stick in your rack) with linux and proprietary software. My gut is that most would find that difficult to swallow. As an aside: I personally feel this has similarity to the google / oracle java lawsuit. If one thinks that APIs cannot be copyrighted then arguably anything that just uses APIs and doesn't embed the actual GPLd code one should be fine as the APIs aren't able to be copyrighted. If on the other hand one views APIs are able to copyrighted as well, then it would be much more clear that the FSF's position is correct. Though the usage might still be fair use (and to an extent one might argue that its even more fair use than Google's usage) If this ever does get litigated, I'll be following closely as would be very interested (intellectually at least) in the result. TLDR: until its actually litigated, everyone who claims to speak an absolute truth is speaking out of their ass. Lawyers are a conservative bunch in general so they'll give you the most conservative answer in terms of what you can do, that doesn't mean its the absolute truth in terms of what you can and cannot do.