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2.6.36-rc1 btrfs still unstable

DISCUSSION Ameya Palande 12 participants 15 messages Aug 16, 2010 – Aug 26, 2010 1 message not in the archive Btrfs file system

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Ameya Palande

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#0 lore raw

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/[email protected]/msg04881.html

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

Thanks!

Cheers,
Ameya.

#1 lore raw
Quoted 11 lines · 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/[email protected]/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

#2 lore raw
Quoted 16 lines · Chris Mason
Quoted 11 lines · 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/[email protected]/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.

Quoted 8 lines

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

#3 lore raw

Hi,

Quoted 4 lines

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.

Signature · 2 lines
Chris Ball   <[email protected]>
One Laptop Per Child

A message that is not in the archive (sent off-list or not yet received): [email protected]

#5 lore raw

I thought this would go to the list automatically.

Here it is now.

---------- Forwarded message ----------
=46rom: Evert Vorster <[email protected]>
Date: Mon, Aug 16, 2010 at 4:04 PM
Subject: Re: 2.6.36-rc1 btrfs still unstable
To: Chris Ball <[email protected]>

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-

Quoted 7 lines · Chris Ball

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?

Quoted 8 lines

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

Quoted 1 line

=A0 While Btrfs is stable on a stable machine, it is currently possib=

le

Quoted 9 lines

=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 <[email protected]>
One Laptop Per Child
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To unsubscribe from this list: send the line "unsubscribe linux-btrfs=

" in

Quoted 3 lines

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#6 lore raw

Hi,

Quoted 1 line

I don't think the signboards are big enough.

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

Quoted 3 lines

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.

Quoted 2 lines

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.

Signature · 2 lines
Chris Ball   <[email protected]>
One Laptop Per Child
#7 lore raw
In reply to Chris Ball

On Lunes, 16 de Agosto de 2010 17:45:29 Chris Ball escribi=F3:

Quoted 2 lines

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

Quoted 2 lines

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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#8 lore raw
Quoted 11 lines

On Lunes, 16 de Agosto de 2010 17:45:29 Chris Ball escribi=C3=B3:

Quoted 6 lines

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
--
Roy Sigurd Karlsbakk
(+47) 97542685
[email protected]
http://blogg.karlsbakk.net/
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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= eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste ti=
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#9 lore raw
Quoted 1 line

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.

#10 lore raw
In reply to Chris Ball
Quoted 5 lines · Chris Ball

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.

#11 lore raw
In reply to Chris Ball
Quoted 2 lines · Chris Ball

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

Quoted 1 line

=C2=A0 to corrupt a filesystem irrecoverably if your machine crashes =

or

Quoted 1 line

=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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#12 lore raw
In reply to Morten P.D. Stevens
Quoted 9 lines · 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

#13 lore raw

Le 25 ao=FBt 2010 =E0 18:57, Johannes Hirte a =E9crit:

Quoted 2 lines
Quoted 2 lines

the other big question is:
Is btrfs with 2.6.36 really rockstable and ready to use in producti=

ve environments?

Quoted 2 lines

=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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#14 lore raw
Quoted 5 lines

Le 25 ao=C3=BBt 2010 =C3=A0 18:57, Johannes Hirte a =C3=A9crit:

Quoted 4 lines
Quoted 3 lines

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

Quoted 8 lines
Quoted 2 lines

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
[email protected]
http://blogg.karlsbakk.net/
--
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Det er et element=C3=A6rt imperativ for alle pedagoger =C3=A5 unng=C3=A5= eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste ti=
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#15 lore raw
In reply to Ameya Palande
Quoted 2 lines · Ameya Palande

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

Signature · 1 line
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC