Re: [linux-lvm] Please help: LVM Recovery on base RHEL3 system.

[Luca Berra <bluca comedia it>]

On Tue, Feb 27, 2007 at 06:04:02PM -0500, Pete Toscano wrote:
> [root Server lvmconf]# cat /proc/mdstat
> Personalities : [raid5]
> read_ahead 1024 sectors
> Event: 1
> md0 : active raid5 hdh[4] hdg[3] hdf[2] hde[1] hdc[0]
>      976793600 blocks level 5, 128k chunk, algorithm 2 [5/5] [UUUUU]
>
> unused devices: <none>
>
> > From what I can tell, though, it doesn't look like LVM is seeing the RAID
> device as a PV anymore:
>
> [root Server lvmconf]# pvdisplay -vv /dev/md0
> pvdisplay -- checking physical volume name "/dev/md0"
> pvdisplay -- reading data of physical volume "/dev/md0" from disk
> pvdisplay -- no physical volume identifier on "/dev/md0"
Weird.
before proceding: are you sure that your friend did not partition the
ide disks before creating the md? could auto-assemble be that stupid?

> I tried to do a vgcfgrestore and got this:
>
> [root Server lvmconf]# vgcfgrestore -n raid_discs -vv  /dev/md0
...
> vgcfgrestore -- ERROR "pv_read(): PV identifier invalid" reading physical
> volume "/dev/md0"
you need to pvcreate the device before using vgcfgrestore, but read the
pvcreate manpage (option -z iirc) or you will do a mess....

> Is there anything that we can do to save his data?  I know that with
> partition tables, if you know them in advance, you can re-write them and, if
> you're exact, you won't lose any data.  Is it possible to do the same with
> pvcreate?  Could I re-init the PV, then have the VG suddenly be happy?
pvcreate/lvcreate by default zeroes the beginning of the PV/LV, you must
use the option -z to avoid this...

> Suggestions?
I would also play with testdisk before pvcreating, but i am pretty sure
that data (or metadata for that matter) does not disappear, so before
doing anything that involves writing to the disk, try understanding what
happened.

L.


--
Luca Berra -- bluca comedia it
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