Using Geom to mirror root partitions?

Josef Karthauser joe at FreeBSD.org
Fri Nov 14 17:41:35 PST 2003


On Sat, Nov 15, 2003 at 12:32:10AM +0100, Poul-Henning Kamp wrote:
> In message <20031114232009.GA31237 at genius.tao.org.uk>, Josef Karthauser writes:
> 
> >I've got a machine with two drives 120gb drives, which is going to a
> >colo.  If I configure it to use one drive, will I at some point be able
> >to remotely reconfigure it to say use the second drive as a mirror as
> >the physical layer, i.e. if the first drive goes bang then I can get the
> >second drive to boot via the bios and still have the machine work - or
> >am I dreaming?
> 
> The main problem here (currently) is the bootblocks and /etc/fstab.
> 
> We had some work on geom_mirror recently which I have not yet had
> time to look at.  If that is done right, it should be possible to
> set it up like you say.
> 
> In order to "fool" the bootblocks, geom_mirror would have to be able
> to use a meta-data sector at the end of the partition rather than at
> the beginning.  With that in place it should "just work", since the
> device in /etc/fstab would then be the geom_mirror device and GEOM
> should be able to offer that for root mounting.
> 

What's the best way to prepare for this?  Should I leave some
unallocated space at the beginning of the disk so that any magic geom
bits can be inserted later?

Joe
-- 
Josef Karthauser (joe at tao.org.uk)	       http://www.josef-k.net/
FreeBSD (cvs meister, admin and hacker)     http://www.uk.FreeBSD.org/
Physics Particle Theory (student)   http://www.pact.cpes.sussex.ac.uk/
================ An eclectic mix of fact and theory. =================
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