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 checks the following
criteria before it alters the VGID:
All raw physical volume devices in the command line have the same
disk type, such as:
- 1)
EMC Symmetrix disks with the BCV attribute. (See EMC documentation.)
- 2)
The XP disk array family with BC_SVOL or CA_SVOL
attributes. (See XP256/XP512 related documentation.)
All raw physical volume devices in the command line belong to the same VG.
(See WARNINGS section.)
Once the checks are successful, the same VGID is set on all the disks. It
should be noted that for multi-PV volume groups all the physical volumes
should be split off and 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
Both the EMC and XP disk arrays have a feature which allows a user
to split off a set of mirror copies of physical volumes (termed
BCVs
or
BCs)
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 (e.g., two out of four disk devices),
the two groups of disk devices would not be able to be imported into the same
VG 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 VG.
If a disk is newly added to an existing volume group
and no subsequent LVM operations has been performed to alter the
structures (i.e., 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 writeable. 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
