Re: reiser4 plugins

[Grzegorz Kulewski]

On Sun, 26 Jun 2005, Alan Cox wrote:

> On Gwe, 2005-06-24 at 20:21, Hans Reiser wrote:
> > Alan, this is FUD.   Our V3 fsck was written after everything else was,
> > for lack of staffing reasons (why write an fsck before you have an FS
> > worth using).  As a result, there was a long period where the fsck code
> > was unstable.  It is reliable now.
> >
> > People often think that our tree makes fsck less robust.  Actually fsck
> > can throw the entire internal tree away and rebuild from leaf nodes, and
> > frankly that makes things pretty robust.
>
> I did a series of tests well after resier3 had fsck that consisted of
> modelling the behaviour of systems under error state. I modelled random
> bit errors, bit errors at a fixed offset (class ram failure), sector 4
> byte slip (known IDE fail case) and sectors going away.
>
> Reiserfs didn't handle it anything like as gracefully as ext2. Its a
> pretty easy experiment to write the code for and the results are
> interesting.

Maybe but I once checked some other error scenario. I generated (by 
mistake of course) dm table that lineary connected 3 times the same 
partition (instead of 3 different partitions). Both Reiser4 and Reiserfs3 
gave a lot of errors while trying to use such device. Ext3 did not give 
single error and was hapily droping my data,

I agree that this is not very useful test case for disk problems but it 
shows that, at least, checks for trouble in Reiser4 are miles before those 
in Ext2/3. If only Reiser4 could print a note what I done wrong... ;-)


Grzegorz Kulewski
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