Date: Thu, 12 Jan 2006 14:23:37 -0700 From: "Kenneth D. Merry" <ken@freebsd.org> To: Peter Jeremy <PeterJeremy@optushome.com.au> Cc: Christoph Kukulies <kuku@www.kukulies.org>, freebsd-hackers@freebsd.org Subject: Re: increasing dd disk to disk transfer rate Message-ID: <20060112212337.GA80216@nargothrond.kdm.org> In-Reply-To: <20060112211300.GB13244@cirb503493.alcatel.com.au> References: <200601120948.k0C9mcqR092895@www.kukulies.org> <20060112211300.GB13244@cirb503493.alcatel.com.au>
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On Fri, Jan 13, 2006 at 08:13:00 +1100, Peter Jeremy wrote: > On Thu, 2006-Jan-12 10:48:38 +0100, Christoph Kukulies wrote: > >dd if=/dev/ad2 of=/dev/ad3 conv=noerror > > > >The process is running now since yesterday evening and it is at 53 MB > >at a transfer rate of about 1.1 MB/s. > > > >In case the the result being unusable I would like to find a way to make this > >copying faster. > > Note that whilst increasing the DD blocksize will speed up the > transfer, it will also increase the amount of collateral damage when a > hard error occurs. If you rummage around the ports or tools tree, > you'll find a utility (its name escapes me but I believe it was > written by phk) that is designed to do disk-to-disk recovery - it > copys data in big slabs until it gets an error and then works around > the faulty area block by block. It's called 'recoverdisk', and is in src/tools/tools/recoverdisk. I used it to copy a friend's hard drive, and it worked well. (Although the supposedly 'bad' disk didn't turn out to have any bad sectors.) Ken -- Kenneth Merry ken@FreeBSD.ORG
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