From owner-freebsd-scsi Mon Jan 31 6:46:11 2000 Delivered-To: freebsd-scsi@freebsd.org Received: from narnia.plutotech.com (narnia.plutotech.com [206.168.67.130]) by hub.freebsd.org (Postfix) with ESMTP id DAD0D14D64 for ; Mon, 31 Jan 2000 06:46:08 -0800 (PST) (envelope-from gibbs@narnia.plutotech.com) Received: (from gibbs@localhost) by narnia.plutotech.com (8.9.3/8.7.3) id HAA32638; Mon, 31 Jan 2000 07:32:31 -0700 (MST) Date: Mon, 31 Jan 2000 07:32:31 -0700 (MST) From: "Justin T. Gibbs" Message-Id: <200001311432.HAA32638@narnia.plutotech.com> To: Greg Lehey Cc: scsi@FreeBSD.org Subject: Re: hardware vs software stripping X-Newsgroups: pluto.freebsd.scsi In-Reply-To: <20000131104827.A62824@freebie.lemis.com> User-Agent: tin/pre-1.4-980818 ("Laura") (UNIX) (FreeBSD/4.0-CURRENT (i386)) Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org In article <20000131104827.A62824@freebie.lemis.com> you wrote: > > I suppose you mean striping. RAID-5 doesn't stripe at the byte level, > it stripes at the block level. RAID-3 stripes at the byte level. I've heard you say this several times, but it is simply not true. RAID-3 is the same as RAID4 without the optimization for partial stripe writes. In otherwords, in RAID-3, you must read or write a full stripe where RAID-4 adds the ability to perform RMW operations on the parity block of the stripe for sub-stripe updates. Pluto uses a RAID-3 system in its video server products and it is certainly not striped on a byte level. (Just as an aside, given the minimum 512 byte sector size of most magnetic media, striping an a per byte basis would be really wasteful). -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message