topic Re: Missing lvol after crash in Operating System - Linux

Missing lvol after crash

Eli_pok — Thu, 31 Aug 2006 08:50:30 GMT

Hi,
After expirencing a crash on a linux Red-Hat 4 As system, one of the lvols has vanished...
The problem is that the /dev/dm files are all there, exept one that was corupted and a new fs was created on it. Unfortuntly, the problem still ocurs on startup saying lvol11 is missing. Another problem that happened after crash was a message about an "open file descriptor".
I would like to know if I can recrate the lvols table acording the dm files ? or there is another solution to the problem ?

Thanks.

Re: Missing lvol after crash

David Child_1 — Thu, 31 Aug 2006 13:38:10 GMT

Interesting... I would take a look at the PV(s) and see what shows up;

1. use vgdisplay -v and get the PV name(s)
2. use 'dd' to write out the header on the disk(s);

dd if=/dev/cciss/c0d0p2 of=/tmp/dd.out count=1 bs=64k

Look for the "logical_volumes" section in /tmp/dd.out. Just verify the LV info is still there for the missing LV.

If it is there then perhaps if you 'vgexport' then 'vgimport' the volume group you can recover it.

David

Re: Missing lvol after crash

Eli_pok — Sun, 03 Sep 2006 01:59:20 GMT

Thanks for the reply....
The problem is that in the system startup the corupted lvol is lvol11 that belongs to vg01 but its file is apsolutly missing....
But if you check the dm files the corupted dm is dm-8 that refers to vg00 and its imposible to do a vgexport to the system vg.
To simplify the problem, all the minor numbers are there, but the connection between the dm files and the lvols is some how broken....
Thanks ahead....

Re: Missing lvol after crash

David Child_1 — Wed, 06 Sep 2006 11:43:04 GMT

Sorry for the late reply.

Okay, I think I understand the problem, but let me make sure;

1. After the crash you no longer see /dev/vg01/lvol11

2. The /dev/dm-8 device for this logical volume is on the box, but it points to one of the logical volumes in vg00

Every time your Linux server reboots it will re-create all the devices in /dev. There is no guarantee that dm-8 = /dev/vg01/lvol11.

Could you post;

1. ls -l /dev/vg01
2. ls -l /dev/mapper/vg01-*
3. ls -l /dev/dm-*
4. vgdisplay -v vg01

This info will help troubleshoot the problem.

Thanks,
David