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



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.


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