From: Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>
To: David Brown <david@westcontrol.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: Is this enough for us to have triple-parity RAID?
Date: Tue, 17 Apr 2012 19:16:09 +0200 [thread overview]
Message-ID: <20120417171609.GA2859@lazy.lzy> (raw)
In-Reply-To: <4F8D228D.8060005@westcontrol.com>
Hi David,
> My current state is that I've got theory worked out and written up -
> not just for triple parity, but for more parities as well. For some
> of it, I've got Python code to test and verify the maths. It turns
> out that triple parity can work well - but for quad parity the limit
> is 21 data disks (using generators 2, 4, and 8), or up to 33 (using
> for example 0x07, 0x35 and 0x8b as generators). Realistically, I
> think triple parity is the limit for practical implementations.
Why is that? An RS code (255,251) should be possible, like
it is a (255,223). What's the limitation?
I'm sure there is even a "RAID-96", which is (96,64).
My wild guess would be that the generators must be chosen
in some way.
Have you had a look at the "par2" code? That seems to be
capable of doing a parametric RS, even if in 16bit words.
bye,
--
piergiorgio
next prev parent reply other threads:[~2012-04-17 17:16 UTC|newest]
Thread overview: 35+ 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 [this message]
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
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
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