From owner-freebsd-questions Thu May 10 6: 4: 5 2001 Delivered-To: freebsd-questions@freebsd.org Received: from guru.mired.org (okc-65-26-235-186.mmcable.com [65.26.235.186]) by hub.freebsd.org (Postfix) with SMTP id 63CF237B422 for ; Thu, 10 May 2001 06:04:03 -0700 (PDT) (envelope-from mwm@mired.org) Received: (qmail 39012 invoked by uid 100); 10 May 2001 13:04:02 -0000 From: Mike Meyer MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15098.37314.356817.228427@guru.mired.org> Date: Thu, 10 May 2001 08:04:02 -0500 To: Chris Fedde Cc: questions@freebsd.org Subject: Re: Use DD to make image copy of dual boot drive? In-Reply-To: <88873791@toto.iv> X-Mailer: VM 6.90 under 21.1 (patch 14) "Cuyahoga Valley" XEmacs Lucid X-face: "5Mnwy%?j>IIV\)A=):rjWL~NB2aH[}Yq8Z=u~vJ`"(,&SiLvbbz2W`;h9L,Yg`+vb1>RG% *h+%X^n0EZd>TM8_IB;a8F?(Fb"lw'IgCoyM.[Lg#r\ Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Chris Fedde types: > On Wed, 9 May 2001 19:35:37 -0500 Mike Meyer wrote: > | > 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. Those typically measure throughput through the file system. In this case, you're not going through the file system. That invalidates the results for this case. http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message