Re: the " 'official' point of view" expressed by kernelnewbies.org regarding reiser4 inclusion

Antonio Vargas
2006-08-04T18:57:59Z

On 8/4/06, Edward Shishkin <edward@namesys.com> wrote:
> Hans Reiser wrote:
> > Edward Shishkin wrote:
> >
> >
> >>Matthias Andree wrote:
> >>
> >>
> >>>On Tue, 01 Aug 2006, Hans Reiser wrote:
> >>>
> >>>
> >>>
> >>>>You will want to try our compression plugin, it has an ecc for every
> >>>>64k....
> >>>
> >>>
> >>>
> >>>What kind of forward error correction would that be,
> >>
> >>
> >>
> >>Actually we use checksums, not ECC. If checksum is wrong, then run
> >>fsck - it will remove the whole disk cluster, that represent 64K of
> >>data.
> >
> >
> > How about we switch to ecc, which would help with bit rot not sector loss?
>
> Interesting aspect.
>
> Yes, we can implement ECC as a special crypto transform that inflates
> data. As I mentioned earlier, it is possible via translation of key
> offsets with scale factor > 1.
>
> Of course, it is better then nothing, but anyway meta-data remains
> ecc-unprotected, and, hence, robustness is not increased..
>
> Edward.
>
> >
> >>
> >> and how much and
> >>
> >>
> >>>what failure patterns can it correct? URL suffices.
> >>>
> >>
> >>Checksum is checked before unsafe decompression (when trying to
> >>decompress incorrect data can lead to fatal things). It can be
> >>broken because of many reasons. The main one is tree corruption
> >>(for example, when disk cluster became incomplete - ECC can not
> >>help here). Perhaps such checksumming is also useful for other
> >>things, I didnt classify the patterns..
> >>
> >>Edward.
> >>
> >>

Would the storage + plugin subsystem support storing >1 copies of the
metadata tree?

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