Re: More info on dd?

From: Alvin Oga (alvin.secat_private-Consulting.com)
Date: Fri Oct 11 2002 - 12:01:41 PDT

  • Next message: Ed Carp: "RE: More info on dd?"

    hi ya
    
    
    copying/cloning a 40GB disk to another 40GB or 60GB or 20GB is
    a good problem...
    
    -- most people assume that there is no bad block on the disks
       when using DD to copy data
    	- if there is a bad block on the master, you copy
    	that to the clone
    
    	- if you have good data in a block on the master, you
    	copy that data to the clone which happens to have a bad block
    	( you lost that tdata .. but wont know about it for a while )
     
    -- dd also copies the entire partition  if you do
    	dd if=/dev/hda1 of=/dev/hdc1
    
    	if the partition is 90% full or fully utilized, it makes sense
    	for dd ... if on the other hand you had 10% used partitions,
    	than you are wasting 90% of your time copying null from 
    	the master to the slave
    
    -- use tar to clone ...  you get a safe copy/clone of the master
    	- if you need a inode-by-inode  clone of the master, than
    	you have no choice but to use dd and hope that your clone
    	does NOT have a bad block
    
    -- cloning a 40 or 60GB disks ( about 8GB of linux installs )
       takes under 20 minutes .... w/ P3-1G..
    
    c ya
    alvin
    
    
    On Fri, 11 Oct 2002, Volker Tanger wrote:
    
    > Greetings!
    > 
    > Ieong Sze Chung Ricci wrote:
    > > 
    > >         However, I could not find any information about the time required
    > > for dd to clone a hard disk of 20G, 30G.
    > > 
    > >         Does any one perform that test before? Can you please share with me
    > > the time required there?
    > 
    > DDing and GZIPping a 40GB disc via 100Mbit/s network 
    > (http://wyae.de/docs/img_dd.php) takes 1-2 hours with a 2MHz P4 on each 
    > side. Slower CPUs probably are better off with COMPRESS or without any 
    > of both.
    > 
    
    
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