[Discuss] Possible backup scenarios for a 500GB drive

[Alan W. Irwin]

On 2007-10-23 20:28-0700 R. Langkamer wrote:

> On 10/23/07 7:45 PM, Alan W. Irwin wrote:
>
>> I am just in the middle of purchasing a new system with a 500GB internal
>> hard drive, and I have heard that a good way to back up large internal
>> drives is with a large external hard drive. Such external hard drives are
>> relatively cheap these days (~$150 for a USB 2.0 500GB external hard drive
>> at atic.ca). One backup scenario I am thinking of is to periodically plug 
>> in
>> a USB external hard drive and run rsync to clone everything under / on the
>> internal drive to the external one.  Would that allow me to boot from
>> the external hard drive as a temporary measure if the internal hard drive
>> failed, and it was taking a while to replace it?
>> 
>> Another backup procedure which I know would work would be to use
>> dump/restore from a rescue distro such as RIP.  (I used that method in the
>> past to restore the club shuttles to a known state after they were loaned
>> out to club members for talks.) However, that method would not allow me to
>> boot during the time when the internal hard drive was being replaced, and
>> I am wondering if the rsync method would actually allow that?
>> 
>> Alan
>
>
> 	While any form of cloning would allow for booting, as far as I know, 
> the boot loader needs to be changed in order for it to load the external 
> volume. For example, while the internal HD has a device ID of /dev/hda1, the 
> external HD would have a device ID of /dev/sda1. Makes sense?

Good point.  As far as the /boot/grub/menu.lst file is concerned, you could
put extra stanzas in there with the alternative ID's, and then use those
alternative stanzas only for the case when you are booting from the clone of
the internal disk on the external drive.  That way avoids the step of having
to edit /boot/grub/menu.lst in the middle of an emergency.  You also have to
set up the MBR of the external disk to point to /boot/grub/menu.lst on that
disk.  I currently don't know how to do that (my initial install of Linux
distros always takes care of it automatically), but I assume it is
straightforward.

John Blomfield posted separately:

> My first thought is that you need a system that has a BIOS that will boot
from a USB if you have nothing on your Hard Drive.  I think such a thing
might exist now??? [...]

Yes.

> Incidentally, if you are buying a new system, if this is a desktop (mini
tower) not a laptop, why not just add a second internal hard drive for
backup?  It will be much faster to backup to that than to an external USB
drive.  USB data transfer is quite slow compared to an internal SATA drive.

I am buying a desktop, and I agree your suggestion is also a good backup
possibility for that case, but one key advantage of external drives is you
can store them off-site to help guard against the case of a fire or some
other office disaster.  Also note that both the rsync and dump/restore
methods are fast (they only deal with changed files after the first use) so
I don't think the speed advantage of internal drives is going to be of
paramount importance.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of
Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
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Linux-powered Science
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