From owner-freebsd-questions Wed May 9 21:19:16 2001 Delivered-To: freebsd-questions@freebsd.org Received: from fedde.littleton.co.us (cfedde.dsl.frii.net [216.17.139.141]) by hub.freebsd.org (Postfix) with ESMTP id E25FA37B422 for ; Wed, 9 May 2001 21:19:12 -0700 (PDT) (envelope-from cfedde@fedde.littleton.co.us) Received: from fedde.littleton.co.us (localhost [127.0.0.1]) by fedde.littleton.co.us (8.11.2/8.11.2) with ESMTP id f4A4J5801430; Wed, 9 May 2001 22:19:05 -0600 (MDT) Message-Id: <200105100419.f4A4J5801430@fedde.littleton.co.us> To: Mike Meyer Cc: "PC Doc" , questions@FreeBSD.ORG Subject: Re: Use DD to make image copy of dual boot drive? In-Reply-To: <15097.57945.106659.703869@guru.mired.org> From: Chris Fedde Date: Wed, 09 May 2001 22:19:05 -0600 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Wed, 9 May 2001 19:35:37 -0500 Mike Meyer wrote: +------------------ | PC Doc types: | > Is copying the whole disk, sector by sector doable with DD? What would the | > command be? I think the 'c' partition refers to the whole disk so I would | > guess something like: | > | > dd if=/dev/rwd0c of=/dev/rw1c bs=??? | | I used to do backups - and run them - that way. On the other hand, | that was a *long* time ago. | | > I'm not sure about the devices and what would be a good block size. Do I | > need to use 512 bytes? The disks say: 32-bit mult-block-16 so that that me an | > an "efficient" block size would be 16x512? Or would a track (63x512) be | > better? | | As long as it's at least 512 bytes, things should work. On the other | hand, the bigger you make it, the faster the copy will go, unless you | force your system to start swapping. I used to do half-cylinder | chunks, because a full cylinder would cause the 11/70 to start | swapping. +------------------ Using one of the dis performance testers like Iozone or bonnie can help you figure out the optomal block size for your system. I've found that about 4096 is optomal for my systems. chris -- Chris Fedde To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message