From owner-freebsd-performance@FreeBSD.ORG Thu Oct 13 00:11:10 2005 Return-Path: X-Original-To: freebsd-performance@FreeBSD.org Delivered-To: freebsd-performance@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0478A16A41F for ; Thu, 13 Oct 2005 00:11:10 +0000 (GMT) (envelope-from wjw@withagen.nl) Received: from freebee.digiware.nl (dsl439.iae.nl [212.61.63.187]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8A64143D46 for ; Thu, 13 Oct 2005 00:11:08 +0000 (GMT) (envelope-from wjw@withagen.nl) Received: from [212.61.27.71] (dual.digiware.nl [212.61.27.71]) by freebee.digiware.nl (Postfix) with ESMTP id 6DD0C2AAAF; Thu, 13 Oct 2005 02:11:07 +0200 (CEST) Message-ID: <434DA6D3.3040309@withagen.nl> Date: Thu, 13 Oct 2005 02:14:11 +0200 From: Willem Jan Withagen User-Agent: Mozilla Thunderbird 1.0.5 (Windows/20050711) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Bruce Evans References: <20051002170446.78674.qmail@web30303.mail.mud.yahoo.com> <004701c5c77e$a8ab4310$b3db87d4@multiplay.co.uk> <434146CA.8010803@pgt.mpt.gov.br> <20051004075806.F45947@delplex.bde.org> In-Reply-To: <20051004075806.F45947@delplex.bde.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Cc: freebsd-performance@FreeBSD.org, =?UTF-8?B?VHVsaW8gR3VpbWFyw6NlcyBkYSBTaWx2YQ==?= Subject: Re: dd(1) performance when copiing a disk to another X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Oct 2005 00:11:10 -0000 Bruce Evans wrote: > On Mon, 3 Oct 2005, [ISO-8859-1] Tulio Guimar�es da Silva wrote: > >> But just to clear out some questions... >> 1) Maxtor�s full specifications for Diamond Max+ 9 Series refers to >> maximum *sustained* transfer rates of 37MB/s and 67MB/s for "ID" and >> "OD", respectively (though I couldn�d find exactly what it means, I >> deduced that represents the rates for center- and border-parts of the >> disk - please correct me if I�m wrong), then your tests show you�re >> getting the best out of it ;) ; >> much slower. > > > Another interesting point is that you can often get closer to the maximum > rate than the average of the maximum and minumum rate. The outer tracks > contain more sectors (about 67/37 times as many with the above spec), so > the average rate over all sectors is larger than average of the max and > min, > significantly so since 67/37 is a fairly large fraction. Also, you can > often partition disks to put less-often accessed stuff in the slow parts. > [All GEOM alligning deleted] As it so happens, I have again some (faster) spare servers in my office. And given the NFS-tests of last year, I want to see if I could run those tests again. But before doing so I wanted to verify the extent of what Bruce suggest here above. (Which I found first in an article some time ago) I've written a small, not yet complete page, on the topic. At current it only involves writting to the disk. But it clearly visualises the effect of non-constant transferrates, which actually depends on the location of the track read from. If you want, you could see for yourself at: http://withagen.dyndns.org/FreeBSD/Performance/Raw-disk/ Suggestions etc. are welcome. --WjW