Date: Fri, 7 Jul 2000 22:27:10 -0500 (CDT) From: "James A. Mutter" <jmutter@colltech.com> To: Emmanuel Gravel <egravel@earthlink.net> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Performance issues with dd Message-ID: <Pine.GSO.4.21.0007072225030.3752-100000@psasolar.private.psa.pencom.com> In-Reply-To: <3966991C.7BB8086A@earthlink.net>
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> 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? > Since you're duplicating an entire disk why not try RAID 0? It's probably a better solution than "dd" and will keep you spare as current as possible. As far as "dd" goes, consider ditching it and using dump/restore, pax, or tar. You may not know it, but "dd" is duplicating the entire disk, bad sectors and all. Good luck, Jim To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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