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Re: dd to clone a drive

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.



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!

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