[CentOS] Recovering LVM volumes

Thu Feb 3 10:58:16 UTC 2011
Sanjay Arora <sanjay.k.arora at gmail.com>

Hello all

I have two sets of eIDE hard drives from earlier servers, one centos &
one fedora. Both were LVM volumes with three or four physical disks,
with ext3 fs. One disk, maybe even the boot one may even be missing,
either from one or both sets and we do not know the disk order. I got
these left from an earlier sysadmin who left the company & nobody know
what's what.

I need to recover data so I need to backup each of the disks to a disk
image file first, then find block-size/recover lvm metadata on the
volume, mount the volume to my current server and recover whatever
files can be recovered manually.

My question is:

- what switches to be used with dd in creating the image, so that I
retain the lvm disk data, for future recovery, if I mess up the
recovery job? Can you please give the actual command assuming disk is
connected at /dev/sdb?

- How do I find the blocksize used by the disk & how do I get the
meta-data and mount the disk to current lvm fs.

Request please give me step by step process. I am finding the howtos &
examples on the net very daunting as most of them have co-issues of
raid etc. Mine is a plain lvm spanning multiple disks.

I don't have expertise of this level & suddenly my boss is expecting
me to perform a miracle.

Please help.

With best regards.
Sanjay.