From owner-freebsd-questions Mon Feb 11 7:42:33 2002 Delivered-To: freebsd-questions@freebsd.org Received: from sage-american.com (sage-american.com [216.122.141.44]) by hub.freebsd.org (Postfix) with ESMTP id 25AA737B405; Mon, 11 Feb 2002 07:42:27 -0800 (PST) Received: from SAGEONE (adsl-64-219-30-160.dsl.crchtx.swbell.net [64.219.30.160]) by sage-american.com (8.9.3/8.9.3) with SMTP id JAA14393; Mon, 11 Feb 2002 09:42:15 -0600 (CST) Message-Id: <3.0.5.32.20020211094213.0195ca18@mail.sage-american.com> X-Sender: jacks@mail.sage-american.com X-Mailer: QUALCOMM Windows Eudora Pro Version 3.0.5 (32) Date: Mon, 11 Feb 2002 09:42:13 -0600 To: "Kevin Oberman" From: jacks@sage-american.com Subject: Re: Using dd to clone HD Cc: Giorgos Keramidas , freebsd-questions@FreeBSD.ORG In-Reply-To: <20020211150814.E61CB5D0C@ptavv.es.net> 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 Yep, I suspect then that the cache is the culprit... couldn't imagine what good 'dd' is if it takes so long.... thanks for the tip. At 07:08 AM 2.11.2002 -0800, Kevin Oberman wrote: >> Date: Sun, 10 Feb 2002 07:56:53 -0600 >> From: jacks@sage-american.com >> Sender: owner-freebsd-questions@FreeBSD.ORG >> >> Thanks for the reply. I went ahead and tried the 'dd' approach using two >> identical 10GB HDs on an experimental box where I wasn't concerned about >> the result just to see what would happen. After more than two hours of >> copying, I decided to abort the process because 10GB is a pretty small HD >> and it would be a very long process to use on the bigger HDs. >> >> Of course the abort trashed the 2nd HD but fixed it with FDISK. Back to the >> drawing board, perhaps with some of your other suggestions. I already use >> tar.... > >I use dd to mirror 2 slices of my hard drive totaling 6 GB. It takes ><14 minutes on my UDMA33 laptop disks. 10GB should not take over 4x as >long! > >Do you have write-cache on? This is HUGE for dd. Turn it off and my 14 >minute copy turns into a >1 hour copy. The performance decreases by >about a factor of 5. Of course, this is very dependent on the exact >hardware (controllers, drives) you use. > >Big block sizes help a lot. I run 32K. 64K would probably be better, >if your geometry will allow it. > >You might also look at the team(1) port. It might allow you to emulate >the disk cache in RAM and restore performance without turning on the >disk write cache. I have seen reports from others that it is quite >effective with dd. > >Since dd copies every block, used or not, it may work better to use >dump/restore for things that are not heavily utilized. But it is far >less efficient, so if anywhere near all of the disk in use, dd will >run much faster. > >R. Kevin Oberman, Network Engineer >Energy Sciences Network (ESnet) >Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) >E-mail: oberman@es.net Phone: +1 510 486-8634 > > > Best regards, Jack L. Stone, Server Admin =================================================== Sage-American http://www.sage-american.com jacks@sage-american.com "My center is giving way, my right is in retreat; ....situation excellent! ....I shall attack!" =================================================== To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message