From owner-freebsd-hackers@FreeBSD.ORG Fri Jan 9 23:59:59 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B76F0106564A for ; Fri, 9 Jan 2009 23:59:59 +0000 (UTC) (envelope-from Danovitsch@vitsch.net) Received: from VM01.VEHosting.nl (unknown [IPv6:2001:470:1f14:32d::1:140]) by mx1.freebsd.org (Postfix) with ESMTP id 7AEBE8FC0C for ; Fri, 9 Jan 2009 23:59:58 +0000 (UTC) (envelope-from Danovitsch@vitsch.net) Received: from [192.168.45.10] (103-241.ftth.onsbrabantnet.nl [88.159.241.103] (may be forged)) (authenticated bits=0) by VM01.VEHosting.nl (8.14.3/8.13.8) with ESMTP id n09Nxvs2060765; Sat, 10 Jan 2009 00:59:57 +0100 (CET) (envelope-from Danovitsch@vitsch.net) From: "Daan Vreeken [PA4DAN]" Organization: Vitsch Electronics To: "M. Warner Losh" Date: Sat, 10 Jan 2009 00:59:48 +0100 User-Agent: KMail/1.9.10 References: <20090109.095027.-1672857892.imp@bsdimp.com> In-Reply-To: <20090109.095027.-1672857892.imp@bsdimp.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200901100059.48906.Danovitsch@vitsch.net> x-ve-auth-version: mi-1.0.3 2008-05-30 - Copyright (c) 2008 - Daan Vreeken - VEHosting x-ve-auth: authenticated as 'pa4dan' on VM01.VEHosting.nl X-Mailman-Approved-At: Sat, 10 Jan 2009 04:21:14 +0000 Cc: freebsd-hackers@freebsd.org Subject: Re: 3x read to write ratio on dump/restore X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 10 Jan 2009 00:00:00 -0000 Hi Warner, On Friday 09 January 2009 17:50:27 M. Warner Losh wrote: > I just copied a disk using dump + restore. I noticed something > through the whole run of this 500GB operation: > > L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name > 3 231 231 14754 9.5 0 0 0.0 97.5| da1s1a > 0 39 0 0 0.0 39 4982 10.0 38.7| da2s1a > > The read kBps was 3x the write kBps. While the dump is going through > the raw device, and the restore is going through the file system, I > can't imagine why we'd have such a huge difference that would be utter > consistent for the whole 15 hour run. > > Any ideas what gives? I observed this with 16MB cache and with 32MB > cache, fwiw. I've noticed this too. Last week I upgraded a laptop harddisk and used dump + restore to copy files from the original harddisk (attached to the laptop using a USB bracket). During the entire copy process I also saw about a 3x difference. -- Daan