Tune2fs metadata_csum

Tune2fs metadata_csum

[Anders Lind]

Hi ext4 developers,


I tired to use tune2fs metadata_csum feature on my ext4 filesystem.
I got message like:
~$ sudo tune2fs -O metadata_csum /dev/sda5
tune2fs 1.42 (29-Nov-2011)
Setting filesystem feature 'metadata_csum' not supported.


Is this tool supposed been used on unmounted device or it could be mounted?


BTW. I googled this problem on internet. Seems no clear answer yet.

Thank you!
Best,

Anders

Re: Tune2fs metadata_csum

[Zheng Liu]

On Sun, Dec 16, 2012 at 08:04:01PM -0800, Anders Lind wrote:
> Hi ext4 developers,
> 
> 
> I tired to use tune2fs metadata_csum feature on my ext4 filesystem.
> I got message like:
> ~$ sudo tune2fs -O metadata_csum /dev/sda5
> tune2fs 1.42 (29-Nov-2011)
> Setting filesystem feature 'metadata_csum' not supported.

Hi Anders,

You need to upgrade your e2fsprogs because metadata_csum feature is
applied on Aug this year.

Regards,
                                                - Zheng

Re: Tune2fs metadata_csum

[Theodore Ts'o]

On Sun, Dec 16, 2012 at 08:04:01PM -0800, Anders Lind wrote:
> 
> I tired to use tune2fs metadata_csum feature on my ext4 filesystem.
> I got message like:
> ~$ sudo tune2fs -O metadata_csum /dev/sda5
> tune2fs 1.42 (29-Nov-2011)
> Setting filesystem feature 'metadata_csum' not supported.
> 
> Is this tool supposed been used on unmounted device or it could be mounted?

TYhe metadata_csum feature is in the e2fsprogs "master" branch in the
e2fsprogs git tree.  The feature is not part of an official e2fsprogs
release yet.  One of the things that I want to really check very
carefully before I release e2fsprogs 1.43 is that e2fsck sanely
recovers from checksum failures while it tries replaying the journal.

Essentially, metadata_csum is supposed to provide better recovery from
device failures (it doesn't really provide any kind of performance
advantage), and I want to be 100% sure that it is **always** better
when hardware-induced corruption happens before we release it.

Regards,

						- Ted

Re: Tune2fs metadata_csum

[Darrick J. Wong]

On Mon, Dec 17, 2012 at 09:37:03AM -0500, Theodore Ts'o wrote:
> On Sun, Dec 16, 2012 at 08:04:01PM -0800, Anders Lind wrote:
> > 
> > I tired to use tune2fs metadata_csum feature on my ext4 filesystem.
> > I got message like:
> > ~$ sudo tune2fs -O metadata_csum /dev/sda5
> > tune2fs 1.42 (29-Nov-2011)
> > Setting filesystem feature 'metadata_csum' not supported.
> > 
> > Is this tool supposed been used on unmounted device or it could be mounted?
> 
> TYhe metadata_csum feature is in the e2fsprogs "master" branch in the
> e2fsprogs git tree.  The feature is not part of an official e2fsprogs
> release yet.  One of the things that I want to really check very
> carefully before I release e2fsprogs 1.43 is that e2fsck sanely
> recovers from checksum failures while it tries replaying the journal.

Oh, right, I /was/ planning (last year) to go dig through recovery.c, wasn't I?
And I think I was going to change the replay/checksum behavior so that checksum
errors would result in that block being skipped, without aborting the entire
replay.

(Or something like that?  My memory is hazy.)

Well, thanks for the reminder.

--D
> 
> Essentially, metadata_csum is supposed to provide better recovery from
> device failures (it doesn't really provide any kind of performance
> advantage), and I want to be 100% sure that it is **always** better
> when hardware-induced corruption happens before we release it.
> 
> Regards,
> 
> 						- Ted
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