Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 04 Jun 2002 14:51:29 +0200 | From | Kasper Dupont <> | Subject | Re: RAID-6 support in kernel? |
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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. For sending spam use mailto:razor-report@daimi.au.dk - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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