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

[gunther.kuhlmann at web.de]

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?
 
> 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
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