Date: Fri, 13 Jan 2006 08:13:00 +1100 From: Peter Jeremy <PeterJeremy@optushome.com.au> To: Christoph Kukulies <kuku@www.kukulies.org> Cc: freebsd-hackers@freebsd.org Subject: Re: increasing dd disk to disk transfer rate Message-ID: <20060112211300.GB13244@cirb503493.alcatel.com.au> In-Reply-To: <200601120948.k0C9mcqR092895@www.kukulies.org> References: <200601120948.k0C9mcqR092895@www.kukulies.org>
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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. You should also install /usr/ports/sysutils/smartmontools - this handles S.M.A.R.T. >Is there a way to tweak the driver (be it the FreeBSD promise driver >or the normal ata driver) to use more retries on errors so that I >have the chance to copy everything or nearly everything of the already >degrading hard disk? A quick look at the ata driver suggests that there are a number of 'retry' and 'retries' variables/fields. I suspect you could increase the number of retries if you wanted to patch the driver. -- Peter Jeremy
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