Date: Mon, 11 Feb 2002 09:42:13 -0600 From: jacks@sage-american.com To: "Kevin Oberman" <oberman@es.net> Cc: Giorgos Keramidas <keramida@FreeBSD.ORG>, freebsd-questions@FreeBSD.ORG Subject: Re: Using dd to clone HD Message-ID: <3.0.5.32.20020211094213.0195ca18@mail.sage-american.com> In-Reply-To: <20020211150814.E61CB5D0C@ptavv.es.net> References: <Your message of "Sun, 10 Feb 2002 07:56:53 CST." <3.0.5.32.20020210075653.0195ca18@mail.sage-american.com>
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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
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