Date: Sat, 8 Jul 2000 11:02:42 +0200 From: Willem Brown <willem@brwn.org> To: Emmanuel Gravel <egravel@earthlink.net> Cc: freebsd-questions@freebsd.org Subject: Re: Performance issues with dd Message-ID: <20000708110241.J30920@snoopy.brwn.org> In-Reply-To: <3966991C.7BB8086A@earthlink.net>; from egravel@earthlink.net on Fri, Jul 07, 2000 at 07:59:40PM -0700 References: <3966991C.7BB8086A@earthlink.net>
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Hi, I used dd once to duplicate disk drive and after a few tries I found that bs=16k was about the quickest. Try playing around with the block size (bs) and see if it makes any difference. There is probably a way calculate this but I don't know about it. Regards Willem Brown On Fri, Jul 07, 2000 at 07:59:40PM -0700, Emmanuel Gravel wrote: > As a backup measure, I'm using two hard drives of the same size, > but only mounting one, and I have a cron job that dd's one to > the other every night. The drives are 18 GB U160 SCSI, on a > AHA-29160N. The whole process takes 45 minutes. A quick calc > tells me it should be finished at best in 2 minutes, at peak > rate. This is over a 20x difference. > > Does anyone have any idea why it's taking so long? Is it just > dd that's the problem? The CPU is a PIII 650, and there's more > than enough memory to go, so I don't think the CPU would be > any kind of an impact here. Is there a better app out there > to do the job? I'm dumping one full raw device to the other, > not individual partitions. Could that be another problem? > > Thanks for any input, I'm at a complete loss here. > > Emmanuel > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message > -- /* =============================================================== */ /* Linux, FreeBSD, NetBSD, OpenBSD. The choice is yours. */ /* =============================================================== */ Hildebrant's Principle: If you don't know where you are going, any road will get you there. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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