From owner-cvs-all Fri Oct 26 17:54:20 2001 Delivered-To: cvs-all@freebsd.org Received: from beppo.feral.com (beppo.feral.com [192.67.166.79]) by hub.freebsd.org (Postfix) with ESMTP id 3861937B403; Fri, 26 Oct 2001 17:54:15 -0700 (PDT) Received: from mailhost.feral.com (mjacob@mailhost.feral.com [192.67.166.1]) by beppo.feral.com (8.11.3/8.11.3) with ESMTP id f9R0sEH13025; Fri, 26 Oct 2001 17:54:14 -0700 (PDT) (envelope-from mjacob@feral.com) Date: Fri, 26 Oct 2001 17:54:14 -0700 (PDT) From: Matthew Jacob X-Sender: mjacob@beppo Reply-To: mjacob@feral.com To: Greg Lehey Cc: Doug Rabson , Luigi Rizzo , John Baldwin , Jonathan Lemon , cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org Subject: Re: RAID-5 parity calculations (was: cvs commit: src/sys/dev/fxp if_fx) In-Reply-To: <20011027102214.C7091@wantadilla.lemis.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Sorry, that seems wrong to me. Typical RAID write performance for something like an Sun A1000 which has a pentium in it is about 50% of theoretical. On Sat, 27 Oct 2001, Greg Lehey wrote: > On Thursday, 25 October 2001 at 15:24:06 -0700, Matt Jacob wrote: > > > > And the fastest software RAID-V I've known was at NASA/Ames on the > > Convex 3280s- they used the otherwise unused vector units for parity > > calculations- this gave write performance for a 22 wide stripe on a > > terabyte fileystem to be at about 88% of theoretical maximum, which > > sure aint' bad. > > The parity calculations for RAID-5 are several orders of magnitude > faster than the disk accesses. Even on a 486, they took hardly any > time. > > Greg > -- > See complete headers for address and phone numbers > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message