Date: Wed, 15 Sep 1999 20:09:58 +0930 From: Greg Lehey <grog@lemis.com> To: Graeme Tait <graeme@echidna.com> Cc: Woody Carey <carey@roguewave.com>, questions@FreeBSD.ORG, andriss@andriss.com, info@boatbooks.com Subject: Re: SCSI drive mirroring question Message-ID: <19990915200957.I30655@freebie.lemis.com> In-Reply-To: <37DF9B61.22D7@echidna.com>; from Graeme Tait on Wed, Sep 15, 1999 at 06:13:05AM -0700 References: <EB55BCC162CAD111BD0A00A0C9979E3201944F1E@cvo1.cvo.roguewave.com> <37DF9B61.22D7@echidna.com>
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On Wednesday, 15 September 1999 at 6:13:05 -0700, Graeme Tait wrote: > Woody Carey wrote: >>> What I want is a true bit by bit mirror of the entire first drive... >>> >>> Can anyone suggest something that would do it? >> >> I was under the impression that 'dd' could be used for bit-by-bit copy. >> Can anyone second this? > > I've used dd successfully to replicate a drive to an identical drive, and > it may well be much faster than file-by-file methods, depending on what > is on the drive to be copied (in particular, how full the drive is). BTW, > I believe this also copies any boot record, etc. > > But this was with the source drive mounted read-only. What would happen > if dd was used to copy a live filesystem, and when the system > wrote a given file, data was written both before and after the current > read point for dd? The data would be inconsistent. That's why we have things like Vinum. Greg -- When replying to this message, please copy the original recipients. For more information, see http://www.lemis.com/questions.html See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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