Mailinglist Archive: opensuse (1556 mails)

[Sampsa Riikonen <sampsa.riikonen@xxxxxx>]

Dear All,

Thank you for your replies to my question.  Here is a summary:

The question was, how to copy an entire hard disk to another hard
disk in a usb box most conveniently.. the command is:

dd if=/dev/sda of=/dev/sdb bs=X

(X=blocksize).

- Herbert recommended a blocksize of 1 Mb (bs=1M)

- Per is using blocksize of 65536 bytes ~ 65 Mb

- Dave warned that blocksize*block should fit in real memory (or is it 
just "blocksize" maybe?).  I have "436593072 blocks" in my /dev/sda3 
partition (according to df).  So with the minimum blocksize of "512" and 
talking in gigabytes, i.e. (436593072*512)/1000000 ~ 223535.. so I should 
have "223535" Gb of memory..?  Something weird here.

- There is a general consensus that eSATA should be more efficient.

- Greg says that 512 (i.e. the default) blocksize works "surprisingly well" 
with raw disks (i.e. with /dev/whatever), but for real files 4Kbytes should 
be used and in the case of tape drives, larger blocksizes are necessary.

(.. some contradictions here with the optimal blocksize).

- Carlos said implicitly that USB might be the bottleneck..  and yes, it is a 
real hard disk and I have a mouse connected to my computer via usb as well.  
According to Carlos'es experience, eSATA is much more "rapido".

.. btw, I have tried to copy my 500Gb hard disk only during ~ 12 hrs (error in 
the original e-mail) with the default 512 byte blocksize, i.e. during the 
night.  In the morning it was still copying.. :(  Well.. I guess I'll try 
tonight again with the 65 Mb blocksize and if that is unacceptable (more than 
one night) I'll be off to by an eSATA thingie for my laptop.

I am very familiar with rsync and I am using it all the time, but I just want
an identical copy of my hard drive every now and then.. just in case.

Regards,

Sampsa
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