fastest raw device copy?

[Jeremy Chadwick]

On Fri, Oct 31, 2008 at 09:48:16AM +0100, Christoph Kukulies wrote:
> Hi list,
>
> I'm considering using a bootable USB stick with FreeBSD to perform a  
> backup of my notebooks'
> 500 GB hard disk to a physically identical (same make, same type, same  
> size) hard disk attached to  USB.
>
> What would be the fastest way to do that sector by sector copy? I'm  
> using dd right now,
>
> dd if=/dev/ad0 of=/dev/da0 bs=10000000
>
> but maybe there is a utility which does this faster or a larger buffer  
> size? Probably the limit will be
> the USB 2.0 bus speed anyway?

In general, what you're doing is correct for a block copy.  There is
nothing (that I know of) which is faster; you're copying 500GB of data
(including the unused portion -- you *did* ask for a block copy),
and this takes a long time.  Be patient.

On the flip side, your blocksize (bs) there is quite high for no good
reason.  I'd pick something more like bs=64k or bs=128k.  The default
(512) is too small for what you want, but 10MBytes is silly.

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |