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vgchgid(1M)

HP-UX 11i Version 3: February 2007
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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 administrator'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

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 group'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

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