From: Goswin von Brederlow <goswin-v-b@web.de>
To: Andre Noll <maan@systemlinux.org>
Cc: Ruslan Sivak <russ@vshift.com>,
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, 18 Mar 2009 15:08:56 +0100 [thread overview]
Message-ID: <87wsam53ev.fsf@frosties.localdomain> (raw)
In-Reply-To: <20090318123525.GK17185@skl-net.de> (Andre Noll's message of "Wed, 18 Mar 2009 13:35:25 +0100")
Andre Noll <maan@systemlinux.org> writes:
> On 08:34, Ruslan Sivak wrote:
>
>> I would guess the reason is that it doesn't make sense. As mentioned, if
>> you are going to create a 3 disk raid 6, it's essentially a raid1 over 3
>> disks, at which point you are better off with the raid-1. I don't think
>> there's a raid controller that would let you set something like this up, I
>> don't see why the softraid should.
>
> Well, Goswin mentioned some pretty good reasons I think.
>
> Andre
> --
> The only person who always got his work done by Friday was Robinson Crusoe
Raid6 is the only level that requires such "sanity".
Here is another scenario: Say you have a 2 disk raid1 and now want to
switch to 5 disk raid6. No problem, add 3 new disks, set up 1+2 disk
raid6, pvmove the data (don't you love LVM?), stop the raid1, grow the
raid6 to 5 disks.
It is clear that 1+2 disk raid6 only makes sense as a transitory step
but one that is usefull.
MfG
Goswin
next prev parent reply other threads:[~2009-03-18 14:08 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 [this message]
2009-03-18 14:26 ` Robin Hill
2009-03-18 18:48 ` Goswin von Brederlow
2009-04-01 16:08 ` H. Peter Anvin
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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