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    SubjectRe: RAID-6 support in kernel?
    Allan Sandfeld wrote:
    >
    > On Monday 03 June 2002 10:57, Kasper Dupont wrote:
    > > Roy Sigurd Karlsbakk wrote:
    > > > > > RAID-6 layout: http://www.acnc.com/04_01_06.html
    > > > >
    > > > > If it is supposed to survive two arbitrary disk failures something is
    > > > > wrong with that figure. They store 12 logical sectors in 20 physical
    > > > > sectors across 4 drives. With two lost disks there are 10 physical
    > > > > sectors left from which we want to reconstruct 12 logical sectors.
    > > > > That is impossible.
    > > >
    > > > Might be the diagram is wrong.
    > >
    > > Could be the case, so until I find another description I will
    > > still not know how RAID-6 works.
    > >
    > It's not just the diagram, the theory is wrong. You need to use at least log2
    > n+1 disks for partition if you want to handle any two lost/borked disks. (16
    > disks would give 11x diskspace).

    But there are other encodings with 2 extra disks that can
    handle 2 lost disks. And in general if you need x disks of
    space and the ability to recover from y lost disks you can
    do the encoding on x+y disks.

    Knowing that why do we even consider RAID-6? I guess RAID-6
    is a lot faster, is that true?

    --
    Kasper Dupont -- der bruger for meget tid på usenet.
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