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