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From: Jon Nelson <jnelson-linux-raid@jamponi.net>
Cc: LinuxRaid <linux-raid@vger.kernel.org>
Subject: Re: unbelievably bad performance: 2.6.27.37 and raid6
Date: Mon, 2 Nov 2009 13:39:35 -0600	[thread overview]
Message-ID: <cccedfc60911021139o7cac1ad2rb70333d5fc8026e6@mail.gmail.com> (raw)
In-Reply-To: <bb145bd20910311259j7b2506c8v4e8907eb73598275@mail.gmail.com>

On Sat, Oct 31, 2009 at 1:59 PM, Christian Pernegger
<pernegger@gmail.com> wrote:
>> md0 : active raid6 sda4[0] sdc4[5] sdd4[4] sdb4[6]
>>      613409536 blocks super 1.1 level 6, 64k chunk, algorithm 2 [4/4] [UUUU]
>
> Why would you use a 4 disk raid6? If 50% of raw capacity is enough
> just go with raid10

With 4 disks, the ability to sustain *any two* devices going bad is a big bonus.
Using raid10 with two copies (1 original, 1 duplicate) on 4 disks
gives me 50% space but I can only sustain *1* failed device. I'm
guessing I'd have to go with raid10 with three copies (1 original, 2
duplicate) which is even worse (2/3 space lost). Did I just calculate
that all wrong?


-- 
Jon
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  reply	other threads:[~2009-11-02 19:39 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-10-31 15:55 unbelievably bad performance: 2.6.27.37 and raid6 Jon Nelson
2009-10-31 18:43 ` Thomas Fjellstrom
2009-11-01 19:37   ` Andrew Dunn
2009-11-01 19:41     ` Thomas Fjellstrom
2009-11-01 23:43       ` NeilBrown
2009-11-01 23:47         ` Thomas Fjellstrom
2009-11-01 23:53           ` Jon Nelson
2009-11-02  2:28             ` Neil Brown
2009-11-01 23:55           ` Andrew Dunn
2009-11-04 14:43           ` CoolCold
2009-10-31 19:59 ` Christian Pernegger
2009-11-02 19:39   ` Jon Nelson [this message]
2009-11-02 20:01     ` Christian Pernegger
2009-11-01  7:17 ` Kristleifur Daðason
2009-11-02 14:54 ` Bill Davidsen
2009-11-02 15:03   ` Jon Nelson
2009-11-03  5:36     ` NeilBrown
2009-11-03  6:09       ` Michael Evans
2009-11-03  6:28         ` NeilBrown
2009-11-03  6:39           ` Michael Evans
2009-11-03  6:46           ` Michael Evans
2009-11-03  9:16             ` NeilBrown
2009-11-03 13:07           ` Goswin von Brederlow
2009-11-03 16:28             ` Michael Evans
2009-11-03 19:26               ` Goswin von Brederlow
2009-11-02 18:51   ` Christian Pernegger

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