[linux-lvm] what happes to VG when disks are added/removed?

[Heinz J . Mauelshagen]

On Tue, Mar 12, 2002 at 08:04:01AM +0100, gunther.kuhlmann at web.de wrote:
> On Mon, Mar 11, 2002, Heinz J . Mauelshagen wrote:
>  
> > > I had two hard disks, the first with three VG's, the second
> > > with one VG (vg2). When the second hard disk started to fail, I
> > > installed a third with VG vg4 and copied the data over. Then,
> > > without deleting vg2, I unplugged hd 2. After reboot, the 
> volume
> > > on vg2 mounted cleanly, although the disk was not available. It
> > > correctly accessed the LV on vg4 on the new disk. Is that 
> correct?
> > > Can I now use either of the two vg2/vg4 to access the LV on the
> > > new disk? How do I get rid of one (and which) without risking 
> my
> > > data? Can I just vgremove vg2 away?
> >
> > Gunther,
> >
> > the result depends on *how* you copied vg2 over to your new hard 
> drive.
> >
> > If you used for eg. dd to do an image copy of the partitions, 
> which contained
> > vg2 on the flaky drive or a whole disk copy keeping sizes, 
> you've got
> +duplicated
> > content and can unplug the flaky device.
> > If you ran vgscan, you saw your 'old' vg2 in the new drive, 
> which is
> > perfectly fine.
>  
> No, I used pvcreate, vgcreate, lvcreate to create vg4 and a LV on 
> it. And than
> rsync to copy the data. That is why I am a bit confused by this 
> behaviour.
> Should I reconnect hd2, then delete vg2 and disconnect hd2 again?

No need to.
You still have /dev/vg2/ device nodes and the new vg4 got the same
internal number so that you can access it through /dev/vg2/*.

Either rename inactive vg4 to vg2 if you want to keep it by
"rm -r /dev/vg2;vgrename vg4 vg2"

or change your fstab to use the /dev/vg4 nodes and remove /dev/vg2/.

/dev/vg2/* is left over, because you didn't remove vg2.

Regards,
Heinz    -- The LVM Guy --

>  
> > BTW: your configuration is a little bit extraordinary in terms 
> of how to use
> > drives as PVs. Typically you shouldn't have multiple VG's on a 
> single drive
> > as you seem to have it.
> > Much rather you should have multiple drives in one VG.
> 
> Yes, I have one HD with two VG's. It might be unusual, but I can't 
> see anything
> wrong with it. I do not intend to span a VG over more than one 
> physical disk,
> because I don't want to have _part_ of a VG to fail. That's when 
> it gets messy.
> I'm not saying it's impossible to recover, I just don't want to 
> try.
> Besides, my HD size is large compared to my LV sizes, that's why I 
> needn't
> bother.
>  
> Gunther
>  
> -- 
> Dipl.-Ing. Gunther Kuhlmann
> gunther_kuhlmann at mentorg.com
> gunther-kuhlmann at easy-call.net
> Tel.: +49 (0)40 / 75 11 84 40
> PGP: E6 BC 78 6B E6 09 C7 16  AB 5D 9A 9A D7 1C 01 FB
> -- 
> 
> 
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*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen at Sistina.com                           +49 2626 141200
                                                       FAX 924446
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