[linux-lvm] Just for information ....
Heinz J . Mauelshagen
mauelshagen at sistina.com
Fri Nov 23 06:07:02 UTC 2001
On Tue, Nov 20, 2001 at 03:06:38PM -0700, Andreas Dilger wrote:
> On Nov 20, 2001 21:41 +0100, Wichert Akkerman wrote:
> > Previously Andreas Dilger wrote:
> > > Yes. You will need to do a vgscan to find the new disks. Hopefully they
> > > will not have the same VG name as another VG on that system.
> >
> > What if they do?
>
> Then it will depend on disk ordering which one you get under that name, and
> the other will be unavailable. vgscan will see all of the disks, but then
> start checking the UUIDs on the PVs against the list on the "first" disk,
> and the extra disks with UUIDs that don't match will be discarded.
Worst case would be a temporary disconnect of the PVs belonging to one
of the VGs which share the same name. vgscan+vgrename the found one and
reconnect the drives and vgscan again.
>
> I don't think there are any likely scenarios with LVM 0.9+ that will cause
> problems, but since UUIDs were only introduced in 0.9, it may be much harder
> to handle this in older LVM versions.
See above.
>
> You might be able to vgexport the disks from the "other" VG at that time,
> and reimport it with a different name, but I don't know how reliable that
> will be (if it even works). LVM has been confused by less.
???
> Better to just
> "not do that" in the first place.
>
> FYI, AIX LVM does not keep the VG name on the disk itself, only a UUID.
> You also never do something like "vgscan" at boot time to reconfigure
> the LVM setup. When you attach the disks to a new system, you have to
> import them (at which point they get a name that is stored in a config
> file in /etc), and your LVM config is never touched until you change it.
> When you export the VG, it also doesn't write to the disks, just deletes
> the config from /etc. This means you don't need to do anything to the
> VG before moving it to another system.
Well, actually you can just "vgscan" in the VG without vgexport'ing it
in Linux LVM as well. vgexport/vgimport exactly is the clean procedure
to make sure that name clashes don't happen!
>
> Cheers, Andreas
> --
> Andreas Dilger
> http://sourceforge.net/projects/ext2resize/
> http://www-mddsp.enel.ucalgary.ca/People/adilger/
>
>
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--
Regards,
Heinz -- The LVM Guy --
*** 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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