From owner-freebsd-stable@FreeBSD.ORG Tue Apr 1 06:23:40 2003 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3BA7D37B401; Tue, 1 Apr 2003 06:23:40 -0800 (PST) Received: from smtpproxy1.mitre.org (smtpproxy1.mitre.org [192.160.51.75]) by mx1.FreeBSD.org (Postfix) with ESMTP id 494C943FAF; Tue, 1 Apr 2003 06:23:39 -0800 (PST) (envelope-from jandrese@mitre.org) Received: from avsrv1.mitre.org (avsrv1.mitre.org [129.83.20.58]) by smtpproxy1.mitre.org (8.12.9/8.12.8) with ESMTP id h31ENaJS001253; Tue, 1 Apr 2003 09:23:37 -0500 (EST) Received: from MAILHUB1 (mailhub1.mitre.org [129.83.20.31]) by smtpsrv1.mitre.org (8.12.9/8.12.8) with ESMTP id h31ENUCg026074; Tue, 1 Apr 2003 09:23:33 -0500 (EST) Received: from mm112324-2k.mitre.org (128.29.3.65) by mailhub1.mitre.org with SMTP id 1741337; Tue, 01 Apr 2003 09:23:28 -0500 Message-ID: <3E89A0DE.7040505@mitre.org> Date: Tue, 01 Apr 2003 09:23:26 -0500 From: Jason Andresen User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.3) Gecko/20030312 X-Accept-Language: en-us, en MIME-Version: 1.0 To: "Greg 'groggy' Lehey" References: <20030330125138.K23911@leelou.in.tern> <3E870CC7.5000204@mac.com> <20030330175605.E23911@leelou.in.tern> <3E87204C.5060304@ludd.luth.se> <3E88524A.1060600@mitre.org> <3E88AECD.10607@liwing.de> <3E88B601.90802@mitre.org> <20030401004953.GE34617@wantadilla.lemis.com> In-Reply-To: <20030401004953.GE34617@wantadilla.lemis.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit cc: FreeBSD Stable List Subject: Re: vinum performance X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 Apr 2003 14:23:40 -0000 Greg 'groggy' Lehey wrote: >>>>I get 4565 K/sec on modern ATA/133 HDDs. >>>> >>>>Reading is much better at 91908 K/sec at least. >> >>Well, I'm writing 200MB files most of the time, so the stripe size is >>not an issue. I'm just wondering why the reads are *20* times faster >>than the writes. > > > They're not. I don't know where you get that read figure from, but no > disk can transfer that fast, and you don't appear to be doing multiple > transfers in parallel. That was what bonnie++ reported. >>I think the read performance was CPU limited in this case. > > > I think you were reading from cache. Quite possible. I'm not sure how bonnie handles that. >>While some of this is probably an oddity with bonnie (Bonnie always >>reports my writes to be about half as fast as the reads, but dd >>thinks otherwise: >> >>(Both of these were on previously untouched files to prevent any >>caching, and the "write" test is on a new file, not rewriting an old one) >>Write speed: >>81920000 bytes transferred in 3.761307 secs (21779663 bytes/sec) >>Read speed: >>81920000 bytes transferred in 3.488978 secs (23479655 bytes/sec) >> >>But on the RAID5: >>Write speed: >>81920000 bytes transferred in 17.651300 secs (4641018 bytes/sec) >>Read speed: >>81920000 bytes transferred in 4.304083 secs (19033090 bytes/sec) > > > Yes, this is very close to the 4:1 ratio that I would expect. If > you're looking for write performance, don't use RAID-5. So FreeBSD never optimizes out those first two operations? I was thinking writing fresh large files to a RAID5 array would only be half as fast as reading. -- \ |_ _|__ __|_ \ __| Jason Andresen jandrese@mitre.org |\/ | | | / _| Network and Distributed Systems Engineer _| _|___| _| _|_\___| Office: 703-883-7755