From: "H. Peter Anvin" <hpa@zytor.com>
To: David Brown <david@westcontrol.com>
Cc: Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>,
linux-raid@vger.kernel.org
Subject: Re: Is this enough for us to have triple-parity RAID?
Date: Thu, 19 Apr 2012 11:16:48 -0700 [thread overview]
Message-ID: <4F905690.3060301@zytor.com> (raw)
In-Reply-To: <4F8DD02F.1060504@westcontrol.com>
On 04/17/2012 01:18 PM, David Brown wrote:
>
> For quad parity, we can try g3 = 8 as the obvious next choice in the
> pattern. Unfortunately, we start hitting conflicts. To recover missing
> data, we have to solve multiple simultaneous equations over G(2⁸), whose
> coefficients depend on the index numbers of the missing disks. With
> parity generators (1, 2, 4, 8), some of these combinations of missing
> disk indexes lead to insoluble equations when you have more that 21 disks.
>
That is because 255 = 3*5*17... this means {02}^3 = {08} is not a generator.
-hpa
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next prev parent reply other threads:[~2012-04-19 18:16 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-17 6:11 Is this enough for us to have triple-parity RAID? Alex
2012-04-17 7:58 ` David Brown
2012-04-17 16:37 ` Stefan /*St0fF*/ Hübner
2012-04-18 14:15 ` Alex
2012-04-18 14:11 ` David Brown
2012-04-17 17:16 ` Piergiorgio Sartor
2012-04-17 20:18 ` David Brown
2012-04-17 20:54 ` Piergiorgio Sartor
2012-04-18 18:22 ` Piergiorgio Sartor
2012-04-18 20:20 ` David Brown
2012-04-18 20:39 ` Piergiorgio Sartor
2012-04-19 18:16 ` H. Peter Anvin [this message]
2012-04-20 2:27 ` Alex
2012-04-20 3:00 ` H. Peter Anvin
2012-04-20 3:32 ` Alex
2012-04-20 18:58 ` David Brown
2012-04-20 19:39 ` H. Peter Anvin
2012-04-20 21:04 ` Piergiorgio Sartor
2012-04-20 21:01 ` Piergiorgio Sartor
2012-04-20 21:29 ` Peter Grandi
2012-04-20 22:31 ` Piergiorgio Sartor
2012-04-21 9:51 ` Peter Grandi
2012-04-21 11:18 ` Piergiorgio Sartor
2012-04-22 3:14 ` Alex
2012-04-22 8:57 ` Piergiorgio Sartor
2012-04-20 7:45 ` Stan Hoeppner
2012-04-23 15:26 ` Alex
2012-04-25 1:20 ` Stan Hoeppner
2012-04-25 2:45 ` Alex
2012-04-25 16:59 ` Emmanuel Noobadmin
2012-04-25 19:29 ` David Brown
2012-04-26 2:30 ` Alex
2012-04-27 15:15 ` Emmanuel Noobadmin
2012-05-01 16:38 ` Alex
2012-04-26 4:24 ` Alex
-- strict thread matches above, loose matches on Subject: below --
2012-04-16 12:55 Alex
2012-04-16 10:04 Alex
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