2.6.36-rc1 btrfs still unstable

2.6.36-rc1 btrfs still unstable

[Ameya Palande]

Hi Chris,

Today I was checking the Kconfig option for btrfs and it still says,
"Btrfs filesystem (EXPERIMENTAL) Unstable disk format"

I remember that some time back we had discussion about this on meego-dev
mailing list:
http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg04881.html

In case if you have forgotten about this, then can we still change this
for 36-rc2?

Thanks!

Cheers,
Ameya.

Re: 2.6.36-rc1 btrfs still unstable

[Chris Mason]

On Mon, Aug 16, 2010 at 11:46:22AM +0300, Ameya Palande wrote:
> Hi Chris,
> 
> Today I was checking the Kconfig option for btrfs and it still says,
> "Btrfs filesystem (EXPERIMENTAL) Unstable disk format"
> 
> I remember that some time back we had discussion about this on meego-dev
> mailing list:
> http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg04881.html
> 
> In case if you have forgotten about this, then can we still change this
> for 36-rc2?

Yes, I'll go ahead and send this one in. 

I've spent a great deal of time trying to nail down the interaction
between raid56 stripe size and adding/removing volumes from the FS
(basically restriping the raid).

The end result just isn't as user friendly as I wanted yet, but the raid
code is holding up very well.

-chris

RE: 2.6.36-rc1 btrfs still unstable

[Morten P.D. Stevens]

On Mon, Aug 16, 2010 at 2:16 PM, Chris Mason <chris.mason@oracle.com> wrote:
>
> On Mon, Aug 16, 2010 at 11:46:22AM +0300, Ameya Palande wrote:
> > Hi Chris,
> >
> > Today I was checking the Kconfig option for btrfs and it still says,
> > "Btrfs filesystem (EXPERIMENTAL) Unstable disk format"
> >
> > I remember that some time back we had discussion about this on meego-dev
> > mailing list:
> > http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg04881.html
> >
> > In case if you have forgotten about this, then can we still change this
> > for 36-rc2?
>
> Yes, I'll go ahead and send this one in.
>
> I've spent a great deal of time trying to nail down the interaction
> between raid56 stripe size and adding/removing volumes from the FS
> (basically restriping the raid).
>
> The end result just isn't as user friendly as I wanted yet, but the raid
> code is holding up very well.
>
> -chris

Hi Chris,

the other big question is:

Is btrfs with 2.6.36 really rockstable and ready to use in productive environments?

Thanks

Morten

Re: 2.6.36-rc1 btrfs still unstable

[Chris Ball]

Hi,

   > the other big question is:
   > 
   > Is btrfs with 2.6.36 really rockstable and ready to use in
   > productive environments?

No, certainly not until there's a working fsck tool -- at the moment
it's rather easy to kill a btrfs by just losing power.

I just added a paragraph to the main page of the wiki about this,
since we've had a few people on IRC express surprise that their
filesystem aren't fixable after power loss.  Feel free to reword:

   Note that Btrfs does not yet have a fsck tool that can fix errors.
   While Btrfs is stable on a stable machine, it is currently possible
   to corrupt a filesystem irrecoverably if your machine crashes or
   loses power.  This will be fixed when the fsck tool is ready.

- Chris.
-- 
Chris Ball   <cjb@laptop.org>
One Laptop Per Child

Fwd: 2.6.36-rc1 btrfs still unstable

[Evert Vorster]

I thought this would go to the list automatically.

Here it is now.


---------- Forwarded message ----------
=46rom: Evert Vorster <evorster@gmail.com>
Date: Mon, Aug 16, 2010 at 4:04 PM
Subject: Re: 2.6.36-rc1 btrfs still unstable
To: Chris Ball <cjb@laptop.org>


I lost a btrfs not long ago, and this is the reason I am on this list.
Lucky for me, I have more than one backup of everything. Most people
that use computers do not. Also, they unplug USB disks without
unmounting, etc....

I don't think the signboards are big enough.

Most people assume that there is some way of fixing a broken file
system, and finding out the btrfs does not have one usually is quite
surprising and just a little too late.

I was under the impression that with atomic writes it's impossible to
mess up a file system?

-Evert-

On Mon, Aug 16, 2010 at 3:45 PM, Chris Ball <cjb@laptop.org> wrote:
> Hi,
>
> =A0 > the other big question is:
> =A0 >
> =A0 > Is btrfs with 2.6.36 really rockstable and ready to use in
> =A0 > productive environments?
>
> No, certainly not until there's a working fsck tool -- at the moment
> it's rather easy to kill a btrfs by just losing power.
>
> I just added a paragraph to the main page of the wiki about this,
> since we've had a few people on IRC express surprise that their
> filesystem aren't fixable after power loss. =A0Feel free to reword:
>
> =A0 Note that Btrfs does not yet have a fsck tool that can fix errors=
=2E
> =A0 While Btrfs is stable on a stable machine, it is currently possib=
le
> =A0 to corrupt a filesystem irrecoverably if your machine crashes or
> =A0 loses power. =A0This will be fixed when the fsck tool is ready.
>
> - Chris.
> --
> Chris Ball =A0 <cjb@laptop.org>
> One Laptop Per Child
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs=
" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at =A0http://vger.kernel.org/majordomo-info.html
>



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Re: 2.6.36-rc1 btrfs still unstable

[Chris Ball]

Hi,

   > I don't think the signboards are big enough.

Sure; that's why I tried to make one of them larger.

   > Most people assume that there is some way of fixing a broken file
   > system, and finding out the btrfs does not have one usually is
   > quite surprising and just a little too late.

Agreed, that's my experience from the IRC channel.

   > I was under the impression that with atomic writes it's
   > impossible to mess up a file system?

Yes, we're not seeing data corruption, we're correctly reporting
that the transid of the data block doesn't match the transid in the
parent node's pointer, which means that some writes went missing.
Then we're hitting a BUG() as a result, which hangs.

I don't know what the right way of dealing with this is going to be,
but answers like "pretend the lost writes never happened and sync the
transids", or "do something other than BUG() on verify_parent_transid()
failure" sound plausible.

- Chris.
-- 
Chris Ball   <cjb@laptop.org>
One Laptop Per Child

Re: 2.6.36-rc1 btrfs still unstable

[Diego Calleja]

On Lunes, 16 de Agosto de 2010 17:45:29 Chris Ball escribi=F3:
>    Note that Btrfs does not yet have a fsck tool that can fix errors.
>    While Btrfs is stable on a stable machine, it is currently possibl=
e
>    to corrupt a filesystem irrecoverably if your machine crashes or
>    loses power.  This will be fixed when the fsck tool is ready.

But doesn't this happen only with cheap disks that don't honour barrier=
s
correctly?
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Re: 2.6.36-rc1 btrfs still unstable

[Chris Samuel]

On 16/08/10 18:46, Ameya Palande wrote:

> Today I was checking the Kconfig option for btrfs and it still says,
> "Btrfs filesystem (EXPERIMENTAL) Unstable disk format"

I have a memory that there was still a possible disk format
change in the pipeline, am I misremembering, Chris M. ?

cheers!
Chris
-- 
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC

Re: 2.6.36-rc1 btrfs still unstable

[Carlos R. Mafra]

On Mo 16.Aug'10 at 11:45:29 -0400, Chris Ball wrote:
> 
>    Note that Btrfs does not yet have a fsck tool that can fix errors.
>    While Btrfs is stable on a stable machine, it is currently possible
>    to corrupt a filesystem irrecoverably if your machine crashes or
>    loses power.  This will be fixed when the fsck tool is ready.

Shouldn't this (surprising) information be in the kernel config option too?

I am testing a btrfs /home on my laptop since January 2010, and somehow
I missed this particular risk. As I knew about the others, I do backups
almost everyday, but anyway.

Re: 2.6.36-rc1 btrfs still unstable

[Rodrigo E. De León Plicet]

On Mon, Aug 16, 2010 at 10:45 AM, Chris Ball <cjb@laptop.org> wrote:
> Note that Btrfs does not yet have a fsck tool that can fix errors.
> =C2=A0 While Btrfs is stable on a stable machine, it is currently pos=
sible
> =C2=A0 to corrupt a filesystem irrecoverably if your machine crashes =
or
> =C2=A0 loses power. =C2=A0This will be fixed when the fsck tool is re=
ady.

Um, is this related to disks lying about actually writing to spinning
rust, or can this happen on disks that do so properly?
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Re: 2.6.36-rc1 btrfs still unstable

[Johannes Hirte]

On Monday 16 August 2010 16:17:54 Morten P.D. Stevens wrote:
> Hi Chris,
> 
> the other big question is:
> 
> Is btrfs with 2.6.36 really rockstable and ready to use in productive environments?
> 
> Thanks
> 
> Morten

I don't think so. There is at least one checksum bug and ENOSPC problems are also still present.

regards,
  Johannes

Re: 2.6.36-rc1 btrfs still unstable

[Xavier Nicollet]

Le 25 ao=FBt 2010 =E0 18:57, Johannes Hirte a =E9crit:
> > the other big question is:
> > Is btrfs with 2.6.36 really rockstable and ready to use in producti=
ve environments?
>=20
> I don't think so. There is at least one checksum bug and ENOSPC probl=
ems are also still present.

I am planning to put 2 dedicated web hosting servers in production
(backuped every day), with 2.6.34.5 vanilla kernel.

I also use btrfs on a 2.6.34 kernel on the backup server (rsync) for
some time.

--=20
Xavier Nicollet
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Re: 2.6.36-rc1 btrfs still unstable

[Roy Sigurd Karlsbakk]

> On Lunes, 16 de Agosto de 2010 17:45:29 Chris Ball escribi=C3=B3:
> >    Note that Btrfs does not yet have a fsck tool that can fix
> >    errors.
> >    While Btrfs is stable on a stable machine, it is currently
> >    possible
> >    to corrupt a filesystem irrecoverably if your machine crashes or
> >    loses power. This will be fixed when the fsck tool is ready.
>=20
> But doesn't this happen only with cheap disks that don't honour
> barriers
> correctly?

Even with cheap drives, a filesystem shouldn't die. With stuff like ZFS=
, you can use all sorts of crap and still live with it. Btrfs should fo=
llow that track.

Vennlige hilsener / Best regards

roy
--
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(+47) 97542685
roy@karlsbakk.net
http://blogg.karlsbakk.net/
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lfeller eksisterer adekvate og relevante synonymer p=C3=A5 norsk.
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Re: 2.6.36-rc1 btrfs still unstable

[Roy Sigurd Karlsbakk]

> Le 25 ao=C3=BBt 2010 =C3=A0 18:57, Johannes Hirte a =C3=A9crit:
> > > the other big question is:
> > > Is btrfs with 2.6.36 really rockstable and ready to use in
> > > productive environments?
> >
> > I don't think so. There is at least one checksum bug and ENOSPC
> > problems are also still present.
>=20
> I am planning to put 2 dedicated web hosting servers in production
> (backuped every day), with 2.6.34.5 vanilla kernel.
>=20
> I also use btrfs on a 2.6.34 kernel on the backup server (rsync) for
> some time.

IMHO using btrfs in production is like playing Russian roulette - it mi=
ght work and can be benifitable, but then, there's another side of the =
coin...

Vennlige hilsener / Best regards

roy
--
Roy Sigurd Karlsbakk
(+47) 97542685
roy@karlsbakk.net
http://blogg.karlsbakk.net/
--
I all pedagogikk er det essensielt at pensum presenteres intelligibelt.=
 Det er et element=C3=A6rt imperativ for alle pedagoger =C3=A5 unng=C3=A5=
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lfeller eksisterer adekvate og relevante synonymer p=C3=A5 norsk.
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Re: 2.6.36-rc1 btrfs still unstable

[Diego Calleja]

> Even with cheap drives, a filesystem shouldn't die. With stuff like ZFS, you can use all sorts of crap and still live with it. Btrfs should follow that track.


Sadly that's not true, a bit of cooperation of the hardware is needed.
Both Btrfs and ZFS need to be sure that certain operations i.e. writting
a modified superblock need to be physically on the disk. Some disks lie
(or fail) when they are asked to write data to the disk, and both filesystems
have faced filesystem inconsistencies due to this. AFAIK there is nothing
the filesystem can do to avoid that.