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Re: Where does LVM store its data?



On Tue, Dec 13, 2005 at 01:25:09PM +0000, Dick Davies wrote:
> On 12/12/05, hendrik@topoi.pooq.com <hendrik@topoi.pooq.com> wrote:
> > Where does LVM store its data -- where it identifies
> > where its logical partitions are.  Can I take a volume
> > that's managed by LVM and physiclaly carry it from one
> > machine to another, and expect the other machine to
> > understand it (assuming its kernel contains LVM support,
> > and assuming the partitions aren't split across physical
> > volumes, of course?)
> >
> > Actually, I suppose I'm asking about LVM2, just in case
> > there is a significant difference.
> 
> As far as I can tell, It's stored in the PVs themselves
> (when I boot ubuntu it finds all my Debian LVs, for example) .

Without, I suppose, reading all your partitions and seeing it there
are files in /etc/lvm.

Thanks.  Now that I think about it, the PVs themselves are the
sensible place to put it.  I wonder if the details are documented
anywhere.

Anyway, I suppose it will be safe to use LVM on a multi-Linux machine.

hendrik

> You should be able to drop a disk in elsewhere
> and have a vgscan/pvscan find it (which happens at boot normally).
> 
> /etc/lvm/lvm.conf mainly configures how pvscan etc work, so unless
> you tweaked that it should'nt be necessary to change it on the other
> box.

Not really another box -- just another Linux with another root partition
on the same box.  Since there seems to be no usable rescue
system with sarge, I'm very much in favour of having another Linux
on another partition on the same machine, which I can use for rescue
attampts.  It's been very useful in the past.

But I suppose that brings up another question -- is it possible to
remote-mount a PV from another machine (perhaps with NFS??) and
get that subsumed under LVM too?  My guess is NO.  Not that I'm planning
to do that...  Remote-mounting a LV shouldn't be any trouble, of course.

-- hendrik



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