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Date:      Sat, 05 May 2001 22:04:58 -0500
From:      Bob Greene <rgreene@tclme.org>
To:        Greg Lehey <grog@lemis.com>
Cc:        "Andrew C. Hornback" <hornback@wireco.net>, Steve Blanzy <sblanzy@aperion.com>, FreeBSD Questions <questions@FreeBSD.ORG>
Subject:   Re: Raid
Message-ID:  <3AF4BF5A.A03D7278@tclme.org>
References:  <000a01c0d57f$2158bb40$0400a8c0@192.168.0.1> <000701c0d581$3dd2da60$0e00000a@tomcat> <20010506101618.B39554@wantadilla.lemis.com>

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Greg Lehey wrote:
> 
> No, RAID-1 gives you the best performance of any RAID setup. The
> reason why you need at least 3 disks for RAID-5 is because it is
> slower, and though it would theoretically work with only two disks,
> it has no advantages over RAID-1 in this configuration.
> 

Huh?  This paragraph makes no sense.

RAID 0 = striped set
RAID 1 = mirrored set
RAID 5 = striped set with parity

RAID 1 gives maximum redundancy, at the cost of two writes.  The third
disk in RAID 5 is not a consequence of performance, it's a requirement
for redundancy.  RAID 5 with only 2 disks is a failure condition of a 3
disk array.  At that point it's effectively just a striped set.

-- 
Bob Greene
rgreene@TclMe.org
Pull my finger for my public key

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