[linux-lvm] Re: Help! snapshot apparenly trashed LVM [recovered? but still Q's]

[ross at biostat.ucsf.edu]

> I did some expanding and shrinking of my volumes and then attempted to
> take a snapshot.  I got an error message that started "Invalid LV in
> extent map".  I now see that message when I do lvscan or pvscan as well.
>
> This looks very bad, and seems to be the same situation as described here:
> http://weblog.pell.portland.or.us/~orc/2008/02/20/000/index.html
>
> Despite these warnings, I *seem* to be able to use my volumes.  However, I
> have stopped doing anything on the system to try to prevent corruption.
>
> First, is it safe to continue to use the system?
>
> Second, what can I do to diagnose or recover?
>
> I'm running a stock Debian 2.6.24 kernel with a single SCSI disk.  Some of
> its partitions are dedicated to an LVM group, out of which most of my
> partitions are carved.  The LVM groups were originally created under EVMS
> with a 2.4 kernel.  I converted them to straight LVM months ago.
>
Following some suggestions in the archive, I used vgcfgrestore -M1 with
the last metadata before the backup, and things seem to be back.  At least
lvscan runs with out errors.

So, 2 new questions:
1) are my data OK? (I'm also curious about what state the system was in
before the recovery--was it safe to use?)

2) how can I take a snapshot without running into this problem?

Thanks.
Ross