From: John Rowe <rowe@excc.ex.ac.uk>
To: linux-raid@vger.kernel.org
Subject: Re: Two-disk RAID5?
Date: Fri, 05 May 2006 10:31:56 +0100 [thread overview]
Message-ID: <1146821517.4365.40.camel@kenny> (raw)
In-Reply-To: <445AA801.6050404@tmr.com>
> Sorry, I couldn't find a diplomatic way to say you're completely wrong.
We don't necessarily expect a diplomatic way, but a clear and
intelligent one would be helpful.
In two-disk RAID5 which is it?
1) The 'parity bit' is the same as the datum.
2) The parity bit is the complement of the datum.
3) It doesn't work at a bit-wise level.
Many of us feel that RAID5 looks like:
parity = data[0];
for (i=1; i < ndisks; ++i)
parity ^= data[i];
which implies (1). It could easily be (2) but merely saying "it's not
data, it's parity" doesn't clarify matters a great deal.
But I'm pleased my question has stirred up such controversy!
John
next prev parent reply other threads:[~2006-05-05 9:31 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-26 18:58 Two-disk RAID5? Jansen, Frank
2006-04-26 19:22 ` Jon Lewis
2006-04-26 22:53 ` Neil Brown
2006-04-27 4:15 ` Al Boldi
2006-05-01 17:11 ` Erik Mouw
2006-05-05 1:18 ` Bill Davidsen
2006-05-05 9:31 ` John Rowe [this message]
2006-05-05 10:03 ` Neil Brown
2006-05-05 10:24 ` Erik Mouw
-- strict thread matches above, loose matches on Subject: below --
2006-04-26 16:41 John Rowe
2006-04-26 17:18 ` Jon Lewis
2006-04-26 18:46 ` Tuomas Leikola
2006-05-05 1:22 ` Bill Davidsen
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