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Re: How well ext3 will tolerate errors?



On Apr 20, 2002  15:31 +0300, Jani Averbach wrote:
> I would like to know how well ext3/(ext2) will tolerate underlaying
> errors (I am planning to use loop-AES backed ext3 fs).

Ext2 (and ext3 by extension) has been in use for a long time, and has
evolved to handle disk errors very well.  However, one of the important
mechanisms for keeping ext2/ext3 robust is that e2fsck is very good at
finding and fixing errors.  Even if you are using ext3 it is still a
good idea to let the mount_count and check_interval counters force
periodic fscks to detect data errors (you can use tune2fs to set the
check intervals).

> So if there is 1024 bytes corruption of data what will be the worst case:
> 
> - If this data belongs to some file, this part of data(file) has been
>   lost?

Correct.

> - If this data belongs to superblock, I have to repair ext3 and use
>   another superblock?

Correct.  e2fsck will do this automatically.

> - If this data belongs to journaling system, I have to ??? or ??? will
>   happen?

At worst the journal recovery will copy a bad block to somewhere else
in the filesystem, and then e2fsck will have to clean it up.

> - If this data is  unused, it will not cause harm at all?

Correct.

Cheers, Andreas
--
Andreas Dilger
http://www-mddsp.enel.ucalgary.ca/People/adilger/
http://sourceforge.net/projects/ext2resize/





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