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List:       freebsd-questions
Subject:    Re: backups & cloning
From:       Polytropon <freebsd () edvax ! de>
Date:       2009-09-30 20:40:34
Message-ID: 20090930224034.3c960afc.freebsd () edvax ! de
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About the dd method:

On Wed, 30 Sep 2009 11:30:58 -0400, Jerry McAllister <jerrymc@msu.edu> wrote:
> It can be used, but it is not a good way to do it.

For regular backups or even for cloning, it's not very
performant, I agree. I'm mostly using this method for
forensic purposes, when I need a copy of a media (a
whole disk, one slice or a particular partition) to toy
around with, so I don't mess up the original data.



> That is because it copies sector by sector and the new 
> disk/filesystem may not match the old exactly. 

That's a known problem. Another problem is time complexity.
The dd program does copy everything - even the unused disk
blocks (which don't need to be copied). This makes this
process often last very long.



> Besides
> when it is newly written on a file by file basis, it can
> be more efficiently laid out and accomodate any changes in
> size and sector addressing.  dd cannot do that.

That's true. This is the point where tools like cpdup and
rsync come into mind (according to creating backups or
clones).



-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...
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