increasing dd disk to disk transfer rate

Kenneth D. Merry ken at
Thu Jan 12 13:23:47 PST 2006

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.)

Kenneth Merry
ken at FreeBSD.ORG

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