From owner-freebsd-questions Mon Sep 30 17:33:41 2002 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7955537B401 for ; Mon, 30 Sep 2002 17:33:40 -0700 (PDT) Received: from sage-one.net (adsl-65-71-135-137.dsl.crchtx.swbell.net [65.71.135.137]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3839043E42 for ; Mon, 30 Sep 2002 17:33:30 -0700 (PDT) (envelope-from jackstone@sage-one.net) Received: from sagea (sagea [192.168.0.3]) by sage-one.net (8.11.6/8.11.6) with SMTP id g910WYN95863; Mon, 30 Sep 2002 19:32:38 -0500 (CDT) (envelope-from jackstone@sage-one.net) Message-Id: <3.0.5.32.20020930193233.028ece30@mail.sage-one.net> X-Sender: jackstone@mail.sage-one.net X-Mailer: QUALCOMM Windows Eudora Pro Version 3.0.5 (32) Date: Mon, 30 Sep 2002 19:32:33 -0500 To: Richard Tobin , "Pranav A. Desai" , From: "Jack L. Stone" Subject: Re: how to use 'dd' to create image of a hard drive? In-Reply-To: <200210010027.BAA18320@sorley.cogsci.ed.ac.uk> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG At 01:27 AM 10.1.2002 +0100, Richard Tobin wrote: >> bs=102400 or bs=128k will dd faster though.... you can play with that. > >That's not my experience. 8k dd runs at disk speed (30-40 MB/s) on >all the machines I've used recently when copying between different >disks on different ATA controllers. Between disks on the same >controller I only get about 13MB/s (why?) but there's no difference >between 8k and 128k dd. > >-- Richard > Check your I/O. Try this: dd if=/dev/ad0c of=/dev/null bs=128k & and in the background do an 'iostat ad0 1'. Here's an example with an IDE drive: # iostat ad0 1 tty ad0 cpu tin tout KB/t tps MB/s us ni sy in id 0 3 5.19 7 0.03 11 0 4 1 84 0 126 127.36 183 22.74 0 0 6 2 92 0 44 128.00 190 23.76 0 0 2 0 98 0 44 128.00 191 23.89 0 0 5 0 95 0 44 128.00 191 23.88 0 0 7 1 92 As you can see, it's really doing 128 kB transfers, for an average transfer rate of almost 24 MB/s Best regards, Jack L. Stone, Administrator SageOne Net http://www.sage-one.net jackstone@sage-one.net To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message