Disk cloning

[Aaron]

On Tue, 20 Jan 2009 16:35:30 +0100
 Renaud MICHEL <renaud.michel.defimedia at gmail.com> wrote:
>Le mardi 20 janvier 2009 à 14:01, Tino Schwarze a écrit :
>> > - recreate or copy MBR to sdb (don't know how)
>>
>> dd if=/dev/sda of=/dev/sdb bs=512 count=1
>
>No, with bs=512 you're gonna overwrite the partition table, which is not 
>what you want, except if you are copying on an identical disk and want 
>exactly the same primary partitions.
>
>You must use bs=446 (the 66 last bytes contains the primary partition table)
>
>-- 
>Renaud MICHEL
>defimedia S.A.
>


In a few of the other messages he said that downtime was not an option, though it was not stated what specifically was running on this machine.

with the example sda, I would assume this is their system disk.  If they have a default install of MySQL for example, this will likely reside on this disk.

dd is not likely an option with anything that locks files or may have live data in buffers/cache.  I would never use dd to clone a live machine that may have files open on the disk in question.

software raid would make far more sense and is easy to set up.  There are many articles on the web showing how to set up a software raid-1 mirror, break the mirror and then restore it elsewhere.