topic Re: Problems with mirrored disks in Operating System - HP-UX

Problems with mirrored disks

Thomas Kopp — Wed, 06 Dec 2000 08:15:45 GMT

Hi,

I work with a hp-ux 10.20 system :

+ root volume (vg00 ; 1 +1 disk - mirrored )
+ applications volume (vg01 ; 1+1 disk -
quorum in use + mirrored )

Backup:
First, I reduce the mirroring for both volumes and used
vgreduce to get only one disk per volume group.
Now for the root volume I used make_recovery -v -A to create a tape.
For the other volume group I used tar cvf ... to create the
second tape.

Restore:
The recovery of the root volume (vg00) was working fine.
But the mirroring of the root-disk had follwing error :
-information in "etc/lvmtab" differs from that in "etc/lvmpvg"
-vgextend: Error detected, when reading from file "etc/lvmpvg"
After deleting "etc/lvmpvg" it works !!

For the mirroring of the vg01-disk I got follwing error :
vgextend: The volume group "/dev/vg01" is not active. Only an active volume group can be extended.

Then I tried to activte this volume.
#vgchange -a y /dev/vg01
vgchange: Couldn't activate volume group "/dev/vg01":
Quorum not present, or some physical volume(s) are missing.

Then I used :
#vgchange -a y -q n /dev/vg01

Activated volume group

vgchange: Couldn't re-synchronize stale partitions of the logical volume:

I/O error

Volume group "/dev/vg01" has been successfully changed.

To extend the volume I used :
#vgextend -g vg01 /dev/vg01 /dev/dsk/c1t3d0
But we got follwing output:
Physical volume group "vg01" has been successfully extended.

vgcfgbackup: /etc/lvmtab is out of date with the running kernel:Kernel indicates 3 disks for "/dev/vg01"; /etc/lvmtab has 2 disks.

Cannot proceed with backup.

Now I used :
#lvreduce -A n -m 0 /dev/vg01/lvol1
#vgreduce -f /dev/vg01
#rm /etc/lvmtab
#vgscan -v

After all this commands, it was now possible to extend +
mirroring the volume.

Question:
Does anybody know, how to work with make_recovery in
such an environment. ( more then one vg +
mirrored disks+quorum )
Thank's in advance!!
Thomas Kopp

Re: Problems with mirrored disks

Carol Garrett — Wed, 06 Dec 2000 08:25:00 GMT

I dont think there is any need to do anything about your mirrored disks when using ignite. We dont here and we have vg00 + vg01 mirrored. We simply use make_recovery for vg00, backup vg01 some other way (fbackup or tar etc) and then boot off the ignite tape, this will restore vg00 (but without the mirrored disk in the vg - only 1 disk in vg00 and no mirroring - turn on the mirroring manually afterwards). After the ignite restore of vg00 it will still know about vg01, simply need to activate vg01 then restore vg01 from backup. Then re-turn on mirroring for vg01 and your done.

Your procedure of reducing the mirrors and reducing the vg's before the ignite restore is overly complicated and only causing problems - as you saw with the kernel and lvm becoming out of sync as to how many disks in vg's. You dont need to do this before running make_recovery.
Ignite doesnt handling mirroring at all - you have to do this yourself after a restore.

Re: Problems with mirrored disks

Dan Hetzel — Wed, 06 Dec 2000 08:46:18 GMT

Hi,

Why do you reduce the mirroring before doing your backup ? You don't need to...

Use make_recovery -A for vg00 and fbackup (or any other suitable tool) for vg01.

You can then boot off the recovery tape, activate vg01 and restore your vg01 data.

You'll have to manually turn mirroring on as Ignite won't do it automatically.

Best regards,

Dan

Re: Problems with mirrored disks

Thomas Kopp — Wed, 06 Dec 2000 09:31:32 GMT

Hi Carol, Hi Dan,

thank's for the quick help.
But, can you tell me something about disk quorum.
Makes quorum any difference during the backup and restore ? ( Can I just ignore it ? )

Thomas

Re: Problems with mirrored disks

Carol Garrett — Wed, 06 Dec 2000 09:55:48 GMT

Hi Thomas,

I would ignore disk quorum. It has no effect on backups and restores that I know of. The only time you have to worry about quorum is if you lose a disk and on reboot the vg wont activate due to quorum not present, and you can get around it anyway by booting with hpux -lq, or if not vg00 then after boot activate a non vg00 vg (eg. vg01) with vhchange -q n

Re: Problems with mirrored disks

Cheryl Griffin — Wed, 06 Dec 2000 13:50:21 GMT

Be sure to check out the mirror documentation for ignite in /opt/ignite/share/doc/diskmirror.pdf

There has also been several posts on this issue. See the following thread which has a script for mirroring attached to the third response.
http://my1.itrc.hp.com/cm/QuestionAnswer/1,1150,0x9602a24d9abcd4118fef0090279cd0f9!0,00.html

Re: Problems with mirrored disks

Dan Hetzel — Wed, 06 Dec 2000 14:31:08 GMT

Hi Kopp,

Quorum has no effects on backup and/or restore.
As far as I know, you can totally ignore it.

If, at boot time, one disk of your root volume group is missing, the system won't boot, as quorum requirement is enforced by default.
You'll have to disable the quorum requirement with 'hpux -lq'

If one disk of any other (non vg00) volume group is missing, you'll have to manually disable quorum requirement with 'vgchange -q n /dev/vgxx'

Best regards,

Dan