Re: dd to clone a drive

[Jack Dangler <tdldev@gmail.com>]

On 09/26/2017 11:35 AM, Gene Heskett wrote:
> On Tuesday 26 September 2017 09:57:57 Jack Dangler wrote:
>
> > I have an existing drive near EOL (judging from the sounds). I got a
> > replacement drive for it (same size).
> >
> > I plugged the replacement into a USB port and started a byte-for-byte
> > copy with
> >
> > dd if=/dev/sda of=/dev/sdc
> >
> > The process ran quietly for almost 30 hours with no discernable
> > results so i killed it. Apparently, it had been running the whole time
> > and resulted in approximately 300 of 500Gb copied. Is it 'usual' to
> > have dd take upwards of 2 days to copy a drive ?
> >
> > The source drive is a 500G 5400rpm WD, and the target is a 500G
> > 7200rpm WD black.
> >
> > Thanks for any input.
> I think when no bs size is specified, it does a sector copy and likely
> verifies it. In writing sd cards in a usb reader/writer here, dd's
> execution time can be cut to maybe 5 minutes for a 2GB image by the use
> of the "bs=4096" option in the above command line.  That should mean
> your 500GB copy operation would take about 20 hours, probably much less
> since the hd can write faster than my sd cards can on a sustained basis
> like 500GB.
>
> > Regards
> >
> > Jack
>
> Cheers, Gene Heskett
Thanks to Roberto Sanchez, Michael Stone, Thomas Schmitt, Pascal 
Hambourg, Michael Stone, and Gene Haskett for the great input! A little 
more reading and a little experimentation, and I've got this working 
well. Changed the process so that each partition was separately cloned, 
but also changed block sizes and made sure that both source and target 
were unmounted. The partitions took far less time than the original, and 
the verification was successful on all. I even cloned my entire 
installation and booted from it to make sure that it, too, would 
function. Thanks again for all the invaluable help!