Latest kernel to use?

Latest kernel to use?

[Sjoerd]

Maybe a silly question for most of you, but the wiki states to always try to 
use the latest kernel with btrfs. Which one would be best: 
- 4.2.1 (currently latest stable and matches the btrfs-progs versioning) or
- the 4.3.x (mainline)?

Stable sounds more stable to me(hence the name ;) ), but the mainline kernel 
seems to be in more active development?

Cheers,
Sjoerd

Re: Latest kernel to use?

[Hugo Mills]

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On Thu, Sep 24, 2015 at 11:07:32PM +0200, Sjoerd wrote:
> Maybe a silly question for most of you, but the wiki states to always try to 
> use the latest kernel with btrfs. Which one would be best: 
> - 4.2.1 (currently latest stable and matches the btrfs-progs versioning) or
> - the 4.3.x (mainline)?
> 
> Stable sounds more stable to me(hence the name ;) ), but the mainline kernel 
> seems to be in more active development?

   I'd suggest sticking to the 4.2 series for now. 4.3 will be in
pre-release state for another couple of months (give or take).

   Hugo.

-- 
Hugo Mills             | In event of Last Trump, please form an orderly queue
hugo@... carfax.org.uk | and await judgement.
http://carfax.org.uk/  |
PGP: E2AB1DE4          |     Unofficial notice in Cambridge University Library

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Re: Latest kernel to use?

[Austin S Hemmelgarn]

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On 2015-09-24 17:07, Sjoerd wrote:
> Maybe a silly question for most of you, but the wiki states to always try to
> use the latest kernel with btrfs. Which one would be best:
> - 4.2.1 (currently latest stable and matches the btrfs-progs versioning) or
> - the 4.3.x (mainline)?
>
> Stable sounds more stable to me(hence the name ;) ), but the mainline kernel
> seems to be in more active development?
>
Like Hugo said, 4.2.1 is what you want right now.  In general, go with 
the highest version number that isn't a -rc version (4.3 isn't actually 
released yet, IIRC they're up to 4.3-rc2 right now, and almost at -rc3) 
(we should probably be specific like this on the wiki).

As far as mainline being under more 'active development', that is 
correct, but to understand why, you have to understand the workflow in 
Linux development.  In general, it goes like this:
1. People send in patches either fixing bugs or adding new features.
2. These get picked up (hopefully) by the individual subsystem 
maintainers, who collect them in their local git repository.
3. When Linus opens the merge window (IOW, right after they release a 
version with a new minor version number), the subsystem maintainers send 
pull requests for him to merge into mainline the patches they've picked up.
4. After the merge window closes, the first -rc (release candidate) for 
the next version gets released, and people start testing.
5. After about a week of testing, people send in bug-fixes (and only bug 
fixes) that then get pulled into the next -rc version.
6. After about 6 to 8 -rc releases, the official release comes out (and 
the merge window for the next version opens).
While all that is happening, bug-fixes that end up in mainline (usually) 
get back-ported to older kernel versions.  Each time one of these 
versions gets a batch of back-ported bug-fixes, the third number in the 
version gets incremented.  So, to sum it up, mainline is where things 
get developed, but the bug-fixes end up in the stable releases anyway.



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Re: Latest kernel to use?

[Rich Freeman]

On Fri, Sep 25, 2015 at 7:20 AM, Austin S Hemmelgarn
<ahferroin7@gmail.com> wrote:
> On 2015-09-24 17:07, Sjoerd wrote:
>>
>> Maybe a silly question for most of you, but the wiki states to always try
>> to
>> use the latest kernel with btrfs. Which one would be best:
>> - 4.2.1 (currently latest stable and matches the btrfs-progs versioning)
>> or
>> - the 4.3.x (mainline)?
>>
>> Stable sounds more stable to me(hence the name ;) ), but the mainline
>> kernel
>> seems to be in more active development?
>>
> Like Hugo said, 4.2.1 is what you want right now.  In general, go with the
> highest version number that isn't a -rc version (4.3 isn't actually released
> yet, IIRC they're up to 4.3-rc2 right now, and almost at -rc3) (we should
> probably be specific like this on the wiki).
>

I'll just say that my btrfs stability has gone WAY up when I stopped
following this advice and instead followed a recent longterm.  Right
now I'm following 3.18.  There were some really bad corruption issues
in 3.17/18/19 that burned me, and today while considering moving up to
4.1 I'm still seeing a lot of threads about issues during balance/etc.
I still run into the odd issue with 3.18, but not nearly to the degree
that I used to.

Now, I would stick with a recent longterm.  The older longterms go
back to a time when btrfs was far more experimental.  Even 3.16
probably has a lot of issues that are fixed in 3.18.

That said, if you do run into an issue on a longterm kernel nobody
around here is likely to be able to help you much unless you can
reproduce it on the most recent stable kernel.

Just tossing that out as an alternative opinion.  Right now I'm
sticking with 3.18, but I'm interested in making the 4.1 switch once
issues with that seem to have died down.

--
Rich

Re: Latest kernel to use?

[Sjoerd]

Thanks all for the feedback. Still doubting though to go for 4.2.1 or not. 
Main reason is that I am currently running 4.1.7 on my laptop which seems to 
work fine and had some issues with the 4.2.0 kernel. No issues I thing that 
were btrfs related, but more related to my nvidia card. Anyway switching back 
to 4.1.7 resolved those, so I am a bit holding back to try the 4.2.1 version 
;)
Anyway I'll see and can always revert back if I don't like it ;)

Cheers,
Sjoerd

Re: Latest kernel to use?

[Roman Mamedov]

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On Fri, 25 Sep 2015 09:12:15 -0400
Rich Freeman <r-btrfs@thefreemanclan.net> wrote:

> I'll just say that my btrfs stability has gone WAY up when I stopped
> following this advice and instead followed a recent longterm.  Right
> now I'm following 3.18.  There were some really bad corruption issues
> in 3.17/18/19 that burned me, and today while considering moving up to
> 4.1 I'm still seeing a lot of threads about issues during balance/etc.
> I still run into the odd issue with 3.18, but not nearly to the degree
> that I used to.
> 
> Now, I would stick with a recent longterm.  The older longterms go
> back to a time when btrfs was far more experimental.  Even 3.16
> probably has a lot of issues that are fixed in 3.18.

Absolutely that! I was pondering whether or not to chime in with my praise of
"longterm" as far as Btrfs stability goes, but apparently it's not just me who
uses it. In my experience 3.18 just works* and is very stable, and before that
it was 3.14, which by luck(?) happened to go longterm IIRC just before Btrfs
transitioned to "kernel worker threads" in 3.15 (and that caused ALL sorts of
trouble initially).

[*] at least in a relatively simple scenario -- with snapshots, but without
using any of the multi-device features or stuff such as qgroups or
send/receive.

-- 
With respect,
Roman

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Re: Latest kernel to use?

[Hugo Mills]

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On Fri, Sep 25, 2015 at 03:36:18PM +0200, Sjoerd wrote:
> Thanks all for the feedback. Still doubting though to go for 4.2.1 or not. 
> Main reason is that I am currently running 4.1.7 on my laptop which seems to 
> work fine and had some issues with the 4.2.0 kernel. No issues I thing that 
> were btrfs related, but more related to my nvidia card. Anyway switching back 
> to 4.1.7 resolved those, so I am a bit holding back to try the 4.2.1 version 
> ;)
> Anyway I'll see and can always revert back if I don't like it ;)

   If 4.1.7 is working OK for you, stick with it. It's getting much
less important now, as btrfs matures, to keep up with the _very_
latest. Purely on gut feeling about issues we see on IRC and here,
3.19 or later would be reasonable at the moment.

   Compared to, say, 3 or 4 years ago when running late -rc kernels
was often preferable to running the latest stable, and things have
improved quite a bit. :)

   Hugo.

-- 
Hugo Mills             | For months now, we have been making triumphant
hugo@... carfax.org.uk | retreats before a demoralised enemy who is advancing
http://carfax.org.uk/  | in utter disorder.
PGP: E2AB1DE4          |                              Eric Frank Russell, Wasp

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Re: Latest kernel to use?

[Bostjan Skufca]

On 25 September 2015 at 15:51, Hugo Mills <hugo@carfax.org.uk> wrote:
> On Fri, Sep 25, 2015 at 03:36:18PM +0200, Sjoerd wrote:
>> Thanks all for the feedback. Still doubting though to go for 4.2.1 or not.
>> Main reason is that I am currently running 4.1.7 on my laptop which seems to
>> work fine and had some issues with the 4.2.0 kernel. No issues I thing that
>> were btrfs related, but more related to my nvidia card. Anyway switching back
>> to 4.1.7 resolved those, so I am a bit holding back to try the 4.2.1 version
>> ;)
>> Anyway I'll see and can always revert back if I don't like it ;)
>
>    If 4.1.7 is working OK for you, stick with it. It's getting much
> less important now, as btrfs matures, to keep up with the _very_
> latest. Purely on gut feeling about issues we see on IRC and here,
> 3.19 or later would be reasonable at the moment.

Similar here: I am sticking with 3.19.2 which has proven to work fine
for me (backup systems with btrfs on lvm, lots of snapshots/subvolumes
and occasional rebalance, no fancy/fresh stuff like btrfs-raid, online
compression or subvolume quota, though this last one is tempting in my
use case).

b.

Re: Latest kernel to use?

[Sjoerd]

On Friday 25 September 2015 13:51:34 Hugo Mills wrote:
> On Fri, Sep 25, 2015 at 03:36:18PM +0200, Sjoerd wrote:
> > Thanks all for the feedback. Still doubting though to go for 4.2.1 or not.
> > Main reason is that I am currently running 4.1.7 on my laptop which seems
> > to work fine and had some issues with the 4.2.0 kernel. No issues I thing
> > that were btrfs related, but more related to my nvidia card. Anyway
> > switching back to 4.1.7 resolved those, so I am a bit holding back to try
> > the 4.2.1 version ;)
> > Anyway I'll see and can always revert back if I don't like it ;)
> 
>    If 4.1.7 is working OK for you, stick with it. It's getting much
> less important now, as btrfs matures, to keep up with the _very_
> latest. Purely on gut feeling about issues we see on IRC and here,
> 3.19 or later would be reasonable at the moment.
> 

OK i'll stick with the longterm 4.1.x branch then..

>    Compared to, say, 3 or 4 years ago when running late -rc kernels
> was often preferable to running the latest stable, and things have
> improved quite a bit. :)

Good to know and thanks for the feedback :)

Cheers,
Sjoerd

Re: Latest kernel to use?

[Rich Freeman]

On Fri, Sep 25, 2015 at 9:25 AM, Bostjan Skufca <bostjan@a2o.si> wrote:
>
> Similar here: I am sticking with 3.19.2 which has proven to work fine for me

I'd recommend still tracking SOME stable series.  I'm sure there were
fixes in 3.19 for btrfs (to say nothing of other subsystems) that
you're missing with that version.  3.19 is also unsupported at this
time.  You might want to consider moving to either 3.18.21 or 4.1.8
and tracking those series instead.  I doubt you'd give up much moving
back to 3.18 and there have been a bunch of btrfs fixes in that series
(though it seems to me that 3.18 has been slower to receive btrfs
patches than some of the other series).

I'm on the fence right now about making the move to 4.1.  Maybe in a
few releases I'll be there, depending on what the noise on the lists
sounds like.

There was a time when you were better off on bleeding-edge linux for
btrfs.  If you REALLY want to run btrfs raid5 or something like that
then I'd say that is still your best strategy.  However, if you stick
with features that have been around for a year the longterm kernels
seem a lot less likely to hit you with a regression, as long as you
don't switch to a new one the day it is declared as such.

--
Rich

Re: Latest kernel to use?

[Bostjan Skufca]

Thanks for heart-warming recommendation, this is also what I generally do.

In this case (and I remember vaguely) the reasoning for going with
3.19.x at the time was that I was hitting some btrfs issues around
3.16 and at the same time eyeing btrfs changesets going into mainline.
This, combined with general recommendation for using latest kernels
for btrfs and that systems were doing backups mainly (so, no
btrfs-related bugs if at all possible, the rest is unimportant),
resulted in what is now stable configuration.

Downgrading - well, no :)

For such systems (backend/backup servers), I tend to upgrade kernels when:
a) some exploit is discovered, or
b) feature present in newer kernel is needed.

I understand the difference between mainline and stable, but I haven't
had problems with mainline 'since forever'.

b.

On 25 September 2015 at 19:00, Rich Freeman <r-btrfs@thefreemanclan.net> wrote:
> On Fri, Sep 25, 2015 at 9:25 AM, Bostjan Skufca <bostjan@a2o.si> wrote:
>>
>> Similar here: I am sticking with 3.19.2 which has proven to work fine for me
>
> I'd recommend still tracking SOME stable series.  I'm sure there were
> fixes in 3.19 for btrfs (to say nothing of other subsystems) that
> you're missing with that version.  3.19 is also unsupported at this
> time.  You might want to consider moving to either 3.18.21 or 4.1.8
> and tracking those series instead.  I doubt you'd give up much moving
> back to 3.18 and there have been a bunch of btrfs fixes in that series
> (though it seems to me that 3.18 has been slower to receive btrfs
> patches than some of the other series).
>
> I'm on the fence right now about making the move to 4.1.  Maybe in a
> few releases I'll be there, depending on what the noise on the lists
> sounds like.
>
> There was a time when you were better off on bleeding-edge linux for
> btrfs.  If you REALLY want to run btrfs raid5 or something like that
> then I'd say that is still your best strategy.  However, if you stick
> with features that have been around for a year the longterm kernels
> seem a lot less likely to hit you with a regression, as long as you
> don't switch to a new one the day it is declared as such.
>
> --
> Rich

Re: Latest kernel to use?

[Duncan]

Bostjan Skufca posted on Fri, 25 Sep 2015 16:34:16 +0200 as excerpted:

> Similar here: I am sticking with 3.19.2 which has proven to work fine
> for me (backup systems with btrfs on lvm, lots of snapshots/subvolumes
> and occasional rebalance, no fancy/fresh stuff like btrfs-raid, online
> compression or subvolume quota, though this last one is tempting in my
> use case).

On that last one, subvolume quota, you've been following list discussion, 
right?  Just in case you haven't...

Btrfs quotas have been an incredibly tough feature to stabilize.  They're 
on the third rewrite and still have some major bugs to fix, so I'd say at 
least a couple more kernel cycles, then check again before using the 
feature.

So, unless you're actively testing and reporting bugs in that specific 
feature (in which case, thanks and please continue! =:^), I continue to 
strongly recommend leaving quotas off for now, as I have been for a year 
or more, now.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman