Date: Sun, 08 Nov 1998 23:23:04 -0700 From: "Justin T. Gibbs" <gibbs@plutotech.com> To: Greg Lehey <grog@lemis.com> Cc: "Justin T. Gibbs" <gibbs@plutotech.com>, "Kenneth D. Merry" <ken@plutotech.com>, bill@bilver.magicnet.net, freebsd-fs@FreeBSD.ORG Subject: Re: RAID-3 and RAID-4 (was: RAID1 Software vs Hardware) Message-ID: <199811090629.XAA25531@pluto.plutotech.com> In-Reply-To: Your message of "Mon, 09 Nov 1998 16:56:12 %2B1030." <19981109165612.K499@freebie.lemis.com>
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>> RAID-3 confines parity to 1 member of the array. The size of the stripe >> is not a part of the specification. In the case of Pluto products, we >> usually use a stripe size of 1MB which implies a per-unit access of >> 1MB/N-1 (N being number of members in the RAID group). > >This looks like RAID-4 to me. Where do you see the difference? RAID-4 adds the ability to do smaller than whole stripe updates with only touching the affected members of the stripe and the parity. RAID-3 concerns itself only with whole strip accesses. Since we have full control over the stripe size and know in advance the type of data we will store and the way it is accessed, RAID-3 is sufficient for Pluto's application. -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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