Re: Checksumming RAID?

[Roy Sigurd Karlsbakk <roy@karlsbakk.net>]

> > If this system is running RAID-6, recovery should be possible to
> > check both parity chunks, right?
> 
> Yes, of course. (And if anyone ever needs it, it is possible to extend
> raid6 to 3 parity chunks. I've done the maths, but it is not
> implemented - there doesn't seem to be a big need for it.) But - again
> referring back to Neil's blog - if the low-level raid spots a
> consistency error, it still cannot correct it reliably even with 2
> parity chunks, and should pass on a read error to the higher level
> raid.
> Using raid6 at the low level would let you do a good consistency check
> even in the case of a failed drive (or a known read error on a drive)
> -
> or two simultaneous undetected read errors. And raid6 on the higher
> level raid would let you correct such errors, even when there are
> other
> errors around. You'd soon reach the point where it is more likely for
> your disks to spontaneously turn into a bowl of petunias than for read
> errors to be undetected or unrecoverable.

That would be nice. So what should be done here in the first place, is to change the code to allow parity data to be read and calculated also on reads?

Vennlige hilsener / Best regards

roy
--
Roy Sigurd Karlsbakk
(+47) 98013356
roy@karlsbakk.net
http://blogg.karlsbakk.net/
GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt
--
I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med xenotyp etymologi. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk.
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html