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Linus Torvalds Doesn't Recommend Using ZFS On Linux

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  • Originally posted by oiaohm View Post
    Yes this include possibly having to rewrite large sections of ZFS under a proper GPL compatible license for Linux or bring back from dead the ZFS for freebsd project.
    FreeBSD is apparently is more comfortable with the CDDL in base than the GPL. (by their total removal of GCC) I probably would be too. License options are a good thing for the world. (unless you're a GNU'er)

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    • Originally posted by oiaohm View Post
      Yes they may use a different approach than Linux does. But the options to deal with having limit cpu and limit memory bandwidth to use are also limited. Any form of abstraction layer causing memory duplication cannot not be tolerated no matter how much coding or legal effect is required to fix it. Yes this include possibly having to rewrite large sections of ZFS under a proper GPL compatible license for Linux or bring back from dead the ZFS for freebsd project.

      The reality here what was the easy way out for ZoL in the past does not work going forwards.
      Can you explain a bit more what you mean here?

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      • Originally posted by k1e0x View Post
        FreeBSD is apparently is more comfortable with the CDDL in base than the GPL. (by their total removal of GCC) I probably would be too. License options are a good thing for the world. (unless you're a GNU'er)
        The License is only one problem. So FreeBSD being more CDDL compadible does not fix the second problem of ZoL that is design.

        Originally posted by aht0 View Post
        Can you explain a bit more what you mean here?
        Simple question aht0 answering it also answer k1e0x question..

        https://github.com/zfsonlinux/zfs/bl...ule/zfs/dbuf.c

        This here is a pure example of design problem. Back in Linux kernel 2.4.10 year 2001 Linux started getting rid of the block layer cache.

        https://www.oreilly.com/library/view...2/ch15s02.html

        Yes it noted back in the old book. Iomap in finishing the job removing the operations from the file system layer that don't effectively use the Linux page cache and large pages work is finishing of the pagecache so there is no reason for a block cache to exist.

        Solaris has a page cache and a block cache so does Illumos.

        Yes freebsd has a block cache between disc and file system as well.
        https://wiki.freebsd.org/BasicVfsConcepts
        But as noted here it design that the VM page cache(the freebsd equal to linux pagecache) is design to share memory pages with the block cache with the page cache.

        Basically both Linux and Freebsd have taken two different routes to nuke the memory duplication between the page cache and the block cache. Linux has gone the step more of reducing the page cache and block cache down to 1 single cache being the Linux page cache.

        That dbuf,c thing really has no place on Freebsd or Linux the way it currently designed. Yes it horrible the correct design there requires platform particular code to take advantage of how Freebsd reduced duplication between its block and page cache or the fact Linux only has a single cache from block devices to file systems to vfs layer

        The concept of being ZFS being able to have it own unique OS independent stack when it comes to handling caching/memory has to end.

        There are other places I can go digging into ZoL that have no place really on freebsd or linux. Maybe they make sense on OS X, Windows and Illumos but they don't make sense at all on Linux and FreeBSD.


        The memory bandwidth limit that the modern hardware hits means the deduplication of storage between VM page cache and the Block cache FreeBSD does or Linux simple reducing down to 1 single cache total is there to reduce memory operations. Reducing memory operations help when your problem is not enough memory bandwidth to go round. Modern hardware pcie has higher transfer rate than your total memory bandwidth.

        Time when ZFS was design the problem was the other way. The world ZFS was designed in the Storage media and the bandwidth from storage to MMU was lower bandwidth than the MMU transfer speed to ram. The world we are in now is inverted to when ZFS was designed so there are a lot of poor design choices that have to go. Mind you those poor design choices could be removable without changing ZFS on disc format but the one thing it should do is nuke the generic OS abstraction layer as a valid idea.
        Last edited by oiaohm; 06 February 2020, 11:03 AM.

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        • Originally posted by Securitex
          Either Oracle or Microsoft (Members of Linux Foundations who pay Linux Foundation and hence pay Linus the salary) like it or not Canonical will be their competitor.
          lol nice observation

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          • Originally posted by unis_torvalds View Post
            ... FreeNAS, a fork of OpenBSD ...
            FreeNAS is a fork of FreeBSD.

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