From: "H. Peter Anvin" <hpa@zytor.com>
To: Andre Noll <maan@systemlinux.org>
Cc: Goswin von Brederlow <goswin-v-b@web.de>, linux-raid@vger.kernel.org
Subject: Re: Why do I need 4 disks for a raid6?
Date: Wed, 01 Apr 2009 09:08:09 -0700 [thread overview]
Message-ID: <49D39169.2050705@zytor.com> (raw)
In-Reply-To: <20090318121825.GL32416@skl-net.de>
Andre Noll wrote:
>
>> So back to my original question: Why does the kernel require 4 disks
>> for a raid6 instead of allowing 3?
>
> Dunno. Maybe Dan, Neil or HPA can tell the reason for imposing this
> limitation.
>
It's very simple: it avoids an ugly corner case in the RAID-6
computation code. Rather than inserting special code (and verifying it,
etc.) to deal with the 3-disk RAID-6 degenerate case, it was easier to
just not permit it.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2009-04-01 16:08 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-17 19:12 Why do I need 4 disks for a raid6? Goswin von Brederlow
2009-03-18 3:41 ` david.geib
2009-03-18 9:50 ` Goswin von Brederlow
2009-03-18 18:12 ` david.geib
2009-03-18 12:18 ` Andre Noll
[not found] ` <49C0EA5F.9070901@vshift.com>
2009-03-18 12:35 ` Andre Noll
2009-03-18 14:08 ` Goswin von Brederlow
2009-03-18 14:26 ` Robin Hill
2009-03-18 18:48 ` Goswin von Brederlow
2009-04-01 16:08 ` H. Peter Anvin [this message]
2009-04-01 17:47 ` Andre Noll
2009-04-01 20:36 ` H. Peter Anvin
2009-04-01 18:07 ` Goswin von Brederlow
2009-04-01 19:05 ` H. Peter Anvin
2009-03-19 23:35 ` Neil Brown
2009-03-20 10:20 ` Goswin von Brederlow
2009-03-23 20:20 ` Nifty Fedora Mitch
2009-03-24 19:32 ` Goswin von Brederlow
2009-04-01 16:09 ` H. Peter Anvin
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