From: Bill Davidsen <davidsen@tmr.com>
To: Erik Mouw <erik@harddisk-recovery.com>
Cc: Jon Lewis <jlewis@lewis.org>,
"Jansen, Frank" <fjansen@egenera.com>,
Tuomas Leikola <tuomas.leikola@gmail.com>,
John Rowe <rowe@excc.ex.ac.uk>,
linux-raid@vger.kernel.org
Subject: Re: Two-disk RAID5?
Date: Thu, 04 May 2006 21:18:57 -0400 [thread overview]
Message-ID: <445AA801.6050404@tmr.com> (raw)
In-Reply-To: <20060501171128.GA18811@harddisk-recovery.com>
Erik Mouw wrote:
>On Wed, Apr 26, 2006 at 03:22:38PM -0400, Jon Lewis wrote:
>
>
>>On Wed, 26 Apr 2006, Jansen, Frank wrote:
>>
>>
>>
>>>It is not possible to flip a bit to change a set of disks from RAID 1 to
>>>RAID 5, as the physical layout is different.
>>>
>>>
>>As Tuomas pointed out though, a 2 disk RAID5 is kind of a special case
>>where all you have is data and parity which is actually also just data.
>>
>>
>
>No, the other way around: RAID1 is a special case of RAID5.
>
No it isn't. If you have N drives in RAID1 you have N independent copies
of the data and no parity, there's just no corresponding thing in RAID5,
which has one copy of the data, plus parity. There is no special case,
it just doesn't work that way. Set N>2 and report back.
Sorry, I couldn't find a diplomatic way to say you're completely wrong.
--
bill davidsen <davidsen@tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
next prev parent reply other threads:[~2006-05-05 1:18 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 [this message]
2006-05-05 9:31 ` John Rowe
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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