Date: Wed, 30 Sep 2009 22:40:34 +0200 From: Polytropon <freebsd@edvax.de> To: Jerry McAllister <jerrymc@msu.edu> Cc: PJ <af.gourmet@videotron.ca>, freebsd-questions@freebsd.org Subject: Re: backups & cloning Message-ID: <20090930224034.3c960afc.freebsd@edvax.de> In-Reply-To: <20090930153058.GC27266@gizmo.acns.msu.edu> References: <4AC29BE6.4000505@videotron.ca> <20090930023051.cff2b0b4.freebsd@edvax.de> <4AC2C104.7090206@videotron.ca> <20090930050805.7f9d7252.freebsd@edvax.de> <20090930153058.GC27266@gizmo.acns.msu.edu>
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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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