Il giorno mercoledì 19 aprile 2017 15:32:44 UTC+2, Rob Morley ha scritto:
> On Wed, 19 Apr 2017 05:41:53 -0700 (PDT)
> jack4747@gmail.com wrote:
> 
> > Il giorno domenica 9 aprile 2017 04:47:48 UTC+2, DisneyWizard the
> > Fantasmic! ha scritto:
> 
> > > dd if=/dev/sdb of=/dev/sda &
> > >   
> > 
> > also the most stupid choice in this case.
> > dd will copy EVERYTHING, even empty space.
> 
> The drive is nearly full, so there won't be much empty space.  If the
> drive is reading one file at a time it will likely have to perform seeks
> in a number of fragmented files (the likelihood of this is increased by
> the fullness of the drive) while dd will read each track consecutively.
> 
> > And also partition table etc. so the result will be a 3TB disk with a
> > 500GB partition, that you then have to expand using parted or similar.
> 
> But copying the whole disk rather than just individual files you don't
> need to format the target drive before copying.

yes, but you end up with a target that has a partition the same size of the
source, even if the target is bigger...

> > Much better (and faster) in this case to mount both HDs and do a cp
> > -a.
> 
> I doubt there's much in it - it's possible dd will be faster because of
> fragmentation.

dd-ing will preserve fragmentation, copying will remove fragmentation.

other cons of dd is that if the copy is interrupted for some reason, it need to
be restarted from the beginning because the target will not be usable until the
end.
With cp at least the copied files are usable.
Better solution would be rsync, so if the copy is interrupted, it will resume
without problem.

Bye Jack

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