Date: Fri, 13 Jan 2006 09:38:58 -0500 From: John Nielsen <lists@jnielsen.net> To: freebsd-hackers@freebsd.org Cc: "Kenneth D. Merry" <ken@freebsd.org>, Christoph Kukulies <kuku@www.kukulies.org>, Peter Jeremy <PeterJeremy@optushome.com.au> Subject: Re: increasing dd disk to disk transfer rate Message-ID: <200601130938.58932.lists@jnielsen.net> In-Reply-To: <20060113132915.GA6848@kukulies.org> References: <200601120948.k0C9mcqR092895@www.kukulies.org> <20060112212337.GA80216@nargothrond.kdm.org> <20060113132915.GA6848@kukulies.org>
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On Friday 13 January 2006 08:29 am, Christoph P. Kukulies wrote: > On Thu, Jan 12, 2006 at 02:23:37PM -0700, Kenneth D. Merry wrote: > > > 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.) > > I was able to recover. The 0.99999980 copy of my damaged disk to the > identical new one, using > > recoverdisk /dev/ad2 /dev/ad3 > > turned out to have been successful. The program was still trying to > improve the result but I didn't see any increase of recoverd block, so I > terminated it. > > Just for the record: Before I wanted to give back in my faulty disk > to my computer supplier as a case for warranty, I zeroed out the faulty > disk. > > dd if=/dev/zero of=/dev/ad2 bs=1m > > It took half an hour to zero out the 80GB. Transferrate 44 MB/s? > And not a single error ? Or is this normal? > > Then I tried to read back > > dd if=/dev/ad2 of=/dev/zero bs=2m > > Yes, just for the fun I said 2m blocksiye. And now we come back > to FreeBSD contents: > > The system froze at this command (FreeBSD 5.2.1 on that machine) I don't know if this is why the system froze, but /dev/zero is probably not a useful output device. You could use of=/dev/null just to see if the disk reads succeed w/o errors. I've also done "cmp /dev/adX /dev/zero" before, but you don't have any control over how the disk reads are handled that way. JN
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