[linux-lvm] Overlapping logical volumes

Heinz J . Mauelshagen mauelshagen at sistina.com
Mon Nov 3 04:11:02 UTC 2003

On Sat, Nov 01, 2003 at 07:07:53PM +1200, Tom Parker wrote:
> Hi,
> I have just experianced a rather nasty bug in lvextend. I grew a logical
> volume and it used extents that were already in use for another logical
> volume.

You're the first reporting.
Do you have abn archive copy in /etc/lvmconf representing that situation still ?
If so, send it to me please <mge at sistina.com>.

> I'm using Debian Woody and Linux 2.4.22 (unpatched Linus kernel.org sources)
> amislave:/# lvextend --help
> Logical Volume Manager 1.0.4
> Heinz Mauelshagen, Sistina Software  02/05/2002 (IOP 10)
> Luckily I noticed the corrupting filesystems fairly quickly and was able to
> mostly recover the situation with minimal losses. Currently I still have the
> two overlapping logical volumes and a lot less trust in the LVM than I had
> before.
> Is there a program that can validate the logical volume configuration and
> ensure that no physical extent is allocated to more the one logical volume?


> When extending a logical volume, or creating a new one, is anything written to
> the newly allocated extents?

While extending, the answer is no.
If creating, the answer is ye, unless you "lvcreate -Zn ...".

> If this were to happen again, and I discovered
> the problem before I made use of the extra space or a new logical volume,
> would I have any corruption of the first logical volume to use the extents in
> question?

As said, use "lvcreate -Zn ..." in order to avoid writing zerores to the first
KB of the new LV (this is necessary because fs mounts can crash your system
otherwise on an un'fscked LV).

> To finish my data recovery, I would like to allocate another large logical
> volume, I'm somewhat wary of doing this without a tool to ensure that the
> group is valid.

Do an "lvcreate -Zn ...", run vgck and check the "lvdisplay -v ..." output
on all your LVs if there's any overlaps again. If so, that's the archive copy
you want to send to me.

> --
> Tom Parker - tom at carrott.org
>            - http://www.carrott.org
> _______________________________________________
> linux-lvm mailing list
> linux-lvm at sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/


Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***


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

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