rsync or dd to clone a hard drive?

Michael D. Setzer II mikes at kuentos.guam.net
Thu Oct 7 23:40:14 UTC 2010


On 7 Oct 2010 at 17:36, Bill Davidsen wrote:

To:             	users at lists.fedoraproject.org
From:           	Bill Davidsen <davidsen at tmr.com>
Subject:        	Re: rsync or dd to clone a hard drive?
Date sent:      	Thu, 07 Oct 2010 17:36:08 -0400
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> Kwan Lowe wrote:
> > On Wed, Oct 6, 2010 at 12:23 PM, Patrick Bartek<bartek047 at yahoo.com>  wrote:
> >> I would use dd to clone (or back up) an entire hard drive.  Easier.  You can even pipe it through gzip to get a compressed image file.
> >
> > I do exactly that... dd piped through gzip then push through an SSH
> > session to a remote where it's extracted and written on the fly to
> > another LV.  I use it to move kvm LVs from machine to machine.  Works
> > great, but there's not much error checking.  If it's critical I do an
> > md5sum on the LVs at the end then compare.
> 

Cut part. 

Some comments on Compression. With my G4L project that backs up and 
restores disk and partitions using dd and compression.  I've also seem 
difference in the speed and load on cpu.  I've used lzop compression as the 
default option do to this.

In a small partition test these were the time results.
10 seconds with no compression
 3 seconds with lzop compression
 6 seconds with gzip compression
18 seconds with bzip compression

With full disk images the same machines take the following.
50 minutes with lzop
100 minutes with gzip

Intestingly, restoring both the lzop and gzip images only takes about 40 
minutes, so compression process takes more load compared to 
uncompressing. 

The general difference between the compression is about 10%. Also, lzop 
only seems to load the CPU at about 30% rather than the 80 - 90% of gzip.

There are lots of things that effect the speed, so this might vary based on the 
overall system and network. 
Good Luck.



> Bill Davidsen <davidsen at tmr.com>
>    "We have more to fear from the bungling of the incompetent than from
> the machinations of the wicked."  - from Slashdot
> 
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+----------------------------------------------------------+
  Michael D. Setzer II -  Computer Science Instructor      
  Guam Community College  Computer Center                  
  mailto:mikes at kuentos.guam.net                            
  mailto:msetzerii at gmail.com
  http://www.guam.net/home/mikes
  Guam - Where America's Day Begins                        
  G4L Disk Imaging Project maintainer 
  http://sourceforge.net/projects/g4l/
+----------------------------------------------------------+

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