Re: SV: RAID-6 support in kernel?

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RAID-6 layout: http://www.acnc.com/04_01_06.html

 > > If it is supposed to survive two arbitrary disk failures something is

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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.

Below is a (patented?) version that works. This is from the linux-raid list

 A1   A2  (P1) (PA)
(P2) (PB)  B2   B1
 C4   C3  (PC) (P3)
(PD) (P4)  D3   D4

Disclaimer: I took that from Patent 6,353,895.  If you look it up you'll see
a lot of different schemes and discussion of XOR-based RAID 6, in language
disguised as English.  You'll also see that I'm listed as the inventor.
That's four companies back for me, but my current employer unknowingly
has some rights to it, so I hope it will see the light of day sometime.

Dale Stephenson
steph@snapserver.com

-- 
Roy Sigurd Karlsbakk, Datavaktmester

Computers are like air conditioners.
They stop working when you open Windows.
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