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Accidentally changed VGID of BCV disks

Sundar G
Frequent Advisor

Accidentally changed VGID of BCV disks

Hi

While trying to attempt for vgimport on a EMC BCV environment+ HP UX 11.31 env, which has around 50 volumes, accidentally i change the VGIDs using vgchgid , in split. So now could not be able to vgimport the vgroup.
Any method to change VGID again/import volumes without issues? or any patch? thanks in advance

-Maha
9 REPLIES
sujit kumar singh
Honored Contributor

Re: Accidentally changed VGID of BCV disks

lakshmi

the vgchgid man page tells that once split the VGID becomes the same after the split vol is merged again .


so do u need to resynchronise ????? not too sure ...


can u detail a bit more ????


sujit
sujit kumar singh
Honored Contributor

Re: Accidentally changed VGID of BCV disks

NAME
vgchgid - modify the Volume Group ID (VGID) on a given set of physical devices
SYNOPSIS
/usr/sbin/vgchgid PhysicalVolumePath [PhysicalVolumePath] ...
DESCRIPTION
The vgchgid command is designed to change the LVM Volume Group ID (VGID) on a supplied set of
disks. vgchgid will work with any type of storage, but it is primarily targeted at disk arrays that are
able to create "snapshots" or "clones" of mirrored LUNs. vgchgid accepts a set of raw physical devices
and ensures that they all belong to the same volume group, before altering the VGID (see WARNINGS section).
The same VGID is set on all the disks and it should be noted that in cases of multi-PV volume groups, all
the physical volumes should be supplied in a single invocation of the vgchgid command.
Options
vgchgid recognizes the following options and arguments:
PhysicalVolumePath The raw devices path name of a physical volume.
Background
Some storage subsystems have a feature which allows a user to split off a set of mirror copies of physical
storage (termed BCVs, BCs, or Snapshots) just as LVM splits off logical volumes with the lvsplit
command. As the result of the "split," the split-off devices will have the same VGID as the original disks.
vgchgid is needed to modify the VGID on the BCV devices. Once the VGID has been altered, the BCV
disks can be imported into a new volume group by using vgimport.
WARNINGS
Once the VGID has been changed, the original VGID is lost until a disk device is re-mirrored with the original
devices. If vgchgid is used on a subset of disk devices (for example, two out of four disk devices), the
two groups of disk devices would not be able to be imported into the same volume group since they have
different VGIDs on them. The solution is to re-mirror all four of the disk devices and re-run vgchgid on
all four BCV devices at the same time, and then use vgimport to import them into the same new volume
group.
If a disk is newly added to an existing volume group and no subsequent LVM operations has been performed
to alter the structures (in other words, operations which perform an automated vgcfgbackup(1M));
then it is possible a subsequent vgchgid will fail. It will report that the disk does not belong to the
volume group. This may be overcome by performing a structure changing operation on the volume group
(for example, using lvcreate).
It is the system administratorâ s responsibility to make sure that the devices provided in the command line
are all Business Copy volumes of the existing standard physical volumes and are in the ready state and
writable. Mixing the standard and BC volumes in the same volume group can cause data corruption.
RETURN VALUE
vgchgid returns the following values:
0 VGID was modified with no error
1 VGID was not modified
EXAMPLES
An example showing how vgchgid might be used:
1. The system administrator uses the following commands to create the Business Continuity (BCV or BC)
copy:
1) For EMC Symmetrix disks, the commands are BCV establish and BCV split.
2) For XP disk array, the commands are paircreate and pairsplit.
Three BCV disks are created.
2. Change the VGID on the BCV disks.
vgchgid /dev/rdsk/c0t0d0 /dev/rdsk/c0t0d1 /dev/rdsk/c0t0d2
624 Hewlett-Packard Company ï ­ï  1 ï ­ï  HP-UX 11i Version 3: February 2007
v
vgchgid(1M) vgchgid(1M)
3. Make a new volume group using the BCV disks.
mkdir /dev/vgbcv
mknod /dev/vgbcv/group c 64 0x040000
4. Import the BCV disks into the new volume group.
vgimport /dev/vgbcv /dev/dsk/c0t0d0 /dev/dsk/c0t0d1 /dev/dsk/c0t0d2
5. Activate the new volume group.
vgchange -a y /dev/vgbcv
6. Backup the new volume groupâ s LVM data structure.
vgcfgbackup /dev/vgbcv
7. Mount the associated logical volumes.
mkdir /bcv/lvol1 /bcv/lvol2
mount /dev/vgbcv/lvol1 /bcv/lvol1
mount /dev/vgbcv/lvol2 /bcv/lvol2
SEE ALSO
vgimport(1M), vgscan(1M), vgcfgbackup
sujit kumar singh
Honored Contributor

Re: Accidentally changed VGID of BCV disks

The manpage says that a BCV (4disks) is split and on one set of the disks (2 disks) u run vgcghid so as to change the VGID for a set of the disks.

Then u create a VG using the disks(2 disks) that u have changed the VGID s and do the backup.

Once u have completed the backup then u again sync the split ones. Once the BCV sync is done that is the have the current data, as u can see the WARNING section of the MANPAGE that tells that once resybc is complete u can run vgchgid on all the disks (4 disks) and then import all of them in the same VG.


please refer the manpagevery cautiously , do not panic, call the backup admins and storage Experts in support immediately.


do not panic



Sujit
Sundar G
Frequent Advisor

Re: Accidentally changed VGID of BCV disks

Thanks Sujit,

So any other way of changing VGID again (i know the disk names) after reboot, sorry for this question.

Thanks

Maha
sujit kumar singh
Honored Contributor

Re: Accidentally changed VGID of BCV disks

hello mahalakshmi,

Please find the information at the folowing link and tell if that is helpful


http://www.knowledgeroot.com/hp-ux/lvm/change-volume-group-id-vgid-of-luns-that-you-have-split-form-a-bc/


sujit
sujit kumar singh
Honored Contributor

Re: Accidentally changed VGID of BCV disks

hello mahalakshmi,

what are the present disks states ? what is the state for the VG ? is it activated and is having a set of disks? are the disks on which u have run the vgchgid still out of the vg? also i need to know the command that use to do the vgimport? does that use the -s option? right now the split disks are in waht state ?

then we can see waht plan can we do for the import?

we can try importing those PVs with the map file but without using the -s flag . That depends if we know whole of the situation and also if that is possible or not....


please elaborate

sujit
sujit kumar singh
Honored Contributor

Re: Accidentally changed VGID of BCV disks

hello, I think the correct way out to recover from this situation is:

1)Remirror all the Devices that were in the VG before the split.
2)after the remirror is over, run the vgchgid simultaneously on all the disks in the single invocation of the vgchgid command line so that they will have the same VGID.
3)Import the devices in the VG.


Sujit
Johnson Punniyalingam
Honored Contributor

Re: Accidentally changed VGID of BCV disks

vgchgid is a command that can be executed before you import the PV in a VG

>>>So any other way of changing VGID again (i know the disk names) after reboot, sorry for this question<<

NO, It cannot be done, becoz you have over written the vgchange id,

You need to start over Again,

(Example)
step1 # After Splitting BCV
=======================

step2 # re-Creating the mirror copies
=============================
lvextend -m1 /dev/vg00/lvol1 /dev/dsk/c1t5d0 --> BCV disk
(follow mirroring for all you logical volumes)

step3 #Now reconfigure the bcv devices
=================================
/bin/mkdir /dev/BCVvg01

/usr/sbin/mknod /dev/BCVvg01/group c 64 0x070000

/usr/sbin/vgchgid /dev/rdsk/c17t0d1

/usr/sbin/vgimport /dev/BCVvg01 /dev/dsk/c17t0d1

/usr/sbin/fsck -F vxfs /dev/BCVvg01/lvol1
/usr/sbin/fsck -F vxfs /dev/BCVvg01/lvol2
/usr/sbin/fsck -F vxfs /dev/BCVvg01/lvol3
/usr/sbin/fsck -F vxfs /dev/BCVvg01/lvol4
/usr/sbin/fsck -F vxfs /dev/BCVvg01/lvol5
/usr/sbin/fsck -F vxfs /dev/BCVvg01/lvol6
/usr/sbin/fsck -F vxfs /dev/BCVvg01/lvol7
/usr/sbin/fsck -F vxfs /dev/BCVvg01/lvol8

/usr/sbin/mount -F vxfs /dev/BCVvg01/lvol1 /BCV/PDN/oradata/db01
/usr/sbin/mount -F vxfs /dev/BCVvg01/lvol2 /BCV/opt/quest
/usr/sbin/mount -F vxfs /dev/BCVvg01/lvol3 /BCV/PDN/oradata/db02
/usr/sbin/mount -F vxfs /dev/BCVvg01/lvol4 /BCV/PRD/SAP
/usr/sbin/mount -F vxfs /dev/BCVvg01/lvol5 /BCV/PDN/oradata/db03
/usr/sbin/mount -F vxfs /dev/BCVvg01/lvol6 /BCV/PDN/oradata/admin
/usr/sbin/mount -F vxfs /dev/BCVvg01/lvol7 /BCV/PDN/oradata/archlog
/usr/sbin/mount -F vxfs /dev/BCVvg01/lvol8 /BCV/PDN/oradata/dba

Thx,
Johnson

Problems are common to all, but attitude makes the difference
Sundar G
Frequent Advisor

Re: Accidentally changed VGID of BCV disks

I contacted EMC Admins, he came to my rescue. I installed EMC Powerpath , EMC admin person asked me to change a flag setting in SPC-3 , then rescan the VG it worked fine. Closing the thread. Thanks a lot Sujith for your encouragement, and suggestions.