Re: Is stability a joke?

[Waxhead <waxhead@online.no>]

Martin Steigerwald wrote:
> Am Sonntag, 11. September 2016, 13:43:59 CEST schrieb Martin Steigerwald:
>>>>> The Nouveau graphics driver have a nice feature matrix on it's webpage
>>>>> and I think that BTRFS perhaps should consider doing something like
>>>>> that
>>>>> on it's official wiki as well
>>>> BTRFS also has a feature matrix. The links to it are in the "News"
>>>> section
>>>> however:
>>>>
>>>> https://btrfs.wiki.kernel.org/index.php/Changelog#By_feature
>>> I disagree, this is not a feature / stability matrix. It is a clearly a
>>> changelog by kernel version.
>> It is a *feature* matrix. I fully said its not about stability, but about
>> implementation – I just wrote this a sentence after this one. There is no
>> need  whatsoever to further discuss this as I never claimed that it is a
>> feature / stability matrix in the first place.
>>
>>>> Thing is: This just seems to be when has a feature been implemented
>>>> matrix.
>>>> Not when it is considered to be stable. I think this could be done with
>>>> colors or so. Like red for not supported, yellow for implemented and
>>>> green for production ready.
>>> Exactly, just like the Nouveau matrix. It clearly shows what you can
>>> expect from it.
> I mentioned this matrix as a good *starting* point. And I think it would be
> easy to extent it:
>
> Just add another column called "Production ready". Then research / ask about
> production stability of each feature. The only challenge is: Who is
> authoritative on that? I´d certainly ask the developer of a feature, but I´d
> also consider user reports to some extent.
>
> Maybe thats the real challenge.
>
> If you wish, I´d go through each feature there and give my own estimation. But
> I think there are others who are deeper into this.
That is exactly the same reason I don't edit the wiki myself. I could of 
course get it started and hopefully someone will correct what I write, 
but I feel that if I start this off I don't have deep enough knowledge 
to do a proper start. Perhaps I will change my mind about this.
>
> I do think for example that scrubbing and auto raid repair are stable, except
> for RAID 5/6. Also device statistics and RAID 0 and 1 I consider to be stable.
> I think RAID 10 is also stable, but as I do not run it, I don´t know. For me
> also skinny-metadata is stable. For me so far even compress=lzo seems to be
> stable, but well for others it may not.
>
> Since what kernel version? Now, there you go. I have no idea. All I know I
> started BTRFS with Kernel 2.6.38 or 2.6.39 on my laptop, but not as RAID 1 at
> that time.
>
> See, the implementation time of a feature is much easier to assess. Maybe
> thats part of the reason why there is not stability matrix: Maybe no one
> *exactly* knows *for sure*. How could you? So I would even put a footnote on
> that "production ready" row explaining "Considered to be stable by developer
> and user oppinions".
>
> Of course additionally it would be good to read about experiences of corporate
> usage of BTRFS. I know at least Fujitsu, SUSE, Facebook, Oracle are using it.
> But I don´t know in what configurations and with what experiences. One Oracle
> developer invests a lot of time to bring BTRFS like features to XFS and RedHat
> still favors XFS over BTRFS, even SLES defaults to XFS for /home and other non
> /-filesystems. That also tells a story.
>
> Some ideas you can get from SUSE releasenotes. Even if you do not want to use
> it, it tells something and I bet is one of the better sources of information
> regarding your question you can get at this time. Cause I believe SUSE
> developers invested some time to assess the stability of features. Cause they
> would carefully assess what they can support in enterprise environments. There
> is also someone from Fujitsu who shared experiences in a talk, I can search
> the URL to the slides again.
By all means, SUSE's wiki is very valuable. I just said that I *prefer* 
to have that stuff on the BTRFS wiki and feel that is the right place 
for it.
>
> I bet Chris Mason and other BTRFS developers at Facebook have some idea on
> what they use within Facebook as well. To what extent they are allowed to talk
> about it… I don´t know. My personal impression is that as soon as Chris went
> to Facebook he became quite quiet. Maybe just due to being busy. Maybe due to
> Facebook being concerned much more about the privacy of itself than of its
> users.
>
> Thanks,