vgextend(1M)

NAME

vgextend — extend an LVM volume group by adding physical volumes

SYNOPSIS

/usr/sbin/vgextend [-f] [-A autobackup] [-g pvg_name] [-x extensibility] [-z sparepv] vg_name pv_path ...

Remarks

vgextend cannot be performed if the volume group is activated in shared mode.

DESCRIPTION

The vgextend command assigns additional physical volumes to volume group vg_name. The volume group must be active.

Volume groups are extended by adding one or more physical volumes specified by pv_path ...

After the physical volumes have been successfully added to the volume group, the disk space they contain can be allocated to logical volumes.

Before assigning an additional physical volume to a volume group, create the physical volume with the pvcreate command (see pvcreate(1M)). Then, create the volume group with the vgcreate command, assigning at least one physical volume (see vgcreate(1M)).

If, for any reason, a specified physical volume cannot be installed into the volume group, an error message is displayed. However, the installation continues to the end of the list of physical volumes.

When a pv_path refers to one of the physical volumes already in the volume group by a different pv_path name to indicate the use of a different controller, this new path becomes an alternate link to the physical volume. When two paths that reference the same disk are provided in the pv_path list, the order of the paths is important. The first path becomes the "primary link" to the physical volume, the second becomes an "alternate link" to the physical volume. The primary link is the path used to access the physical volume unless the primary link becomes unavailable in which case LVM automatically switches to the alternate link to access the physical volume (see WARNINGS section). Currently LVM supports a maximum of 8 paths to a physical volume (7 alternates and one primary).

Options and Arguments

vgextend recognizes the following options and arguments:

pv_path

The block device path name of a physical volume.

vg_name

The path name of the volume group.

-A autobackup

Set automatic backup for this invocation of this command. autobackup can have one of the following values:

y

Automatically back up configuration changes made to the volume group. This is the default.

After this command executes, the vgcfgbackup command (see vgcfgbackup(1M)) is executed for the volume group.

n

Do not back up configuration changes this time.

-f

Forcibly extend the volume group with a physical volume which has alternate block(s) already allocated, (in other words, this physical volume was not initialized using pvcreate -f.) This option should be used with extreme caution. If the disk is being extended to a volume group with a different physical extent size, the alternate block(s) might be inside the user data area. Potential data corruption could occur.

-g pvg_name

Extend an existing physical volume group while the volume group is being extended by adding all the physical volumes in the pv_path parameter to the physical volume group specified by pvg_name.

If the specified physical volume group does not exist, it is created, thus providing a means for creating new physical volume groups after the volume group has been created. Another way to extend or add a physical volume group is to edit the /etc/lvmpvg file as described in vgcreate(1M). See lvmpvg(4) for format details.

-x extensibility

Set allocation permission for additional physical extents on the physical volume specified by pv_path. extensibility can have one of the following values:

y: Allow allocation of additional physical extents on the physical volume.
n: Prohibit allocation of additional physical extents on the physical volume. Logical volumes residing on the physical volume can still be accessed.

-z sparepv

This option requires the installation of the optional HP MirrorDisk/UX software. It allows you to mark the physical volume(s) specified by pv_path to be either a spare physical volume or a regular, non-spare physical volume. (A spare physical volume can be used to replace an existing physical volume within a volume group when mirroring is in effect, in the event the existing physical volume fails.) sparepv can have one of the following values:

y: The physical volume(s) will be used as spare(s). No physical extents from a spare physical volume will be available as part of the "free" pool of extents in the volume group. The spare physical volume(s) will only be used in the event of another physical volume within this volume group becomes unavailable (fails).
n: The physical volume(s) will be used as regular, non-spare members of the volume group. This is the default.

Alternate Links (PVLinks)

In this release of HP-UX, LVM continues to support Alternate Links to a device to allow continued access to the device, if the primary link fails. This multiple link or multipath solution increases data availability, but does not allow the multiple paths to be used simultaneously.

There is a new feature introduced in the Mass Storage Subsystem on this version of HP-UX that also supports multiple paths to a device and allows access to the multiple paths simultaneously. The Mass Storage Subsystem will balance the I/O load across the valid paths. This new multi-path behavior is enabled and disabled through the use of the scsimgr command. See scsimgr(1M) for details.

It is no longer required or recommended to configure LVM with alternate links. However, it is possible to maintain the traditional LVM behavior. To do so, both of the following criteria must be met:

Only the legacy device special file naming convention is used in the volume group configuration.
The scsimgr command is used to disable the Mass Storage Subsystem multipath behavior.

EXTERNAL INFLUENCES

Environment Variables

LANG determines the language in which messages are displayed.

If LANG is not specified or is null, it defaults to "C" (see lang(5)).

If any internationalization variable contains an invalid setting, all internationalization variables default to "C" (see environ(5)).

EXAMPLES

Add physical volumes /dev/dsk/c0t1d0 and /dev/dsk/c0t2d0 to volume group /dev/vg03:

vgextend /dev/vg03 /dev/dsk/c0t1d0 /dev/dsk/c0t2d0 

Extend physical volume group PVG0 while adding physical volumes /dev/dsk/c0t3d0 and /dev/dsk/c0t4d0 to volume group /dev/vg03:

vgextend -g PVG0 /dev/vg03 /dev/dsk/c0t3d0 /dev/dsk/c0t4d0 

Add an alternate link to one of the physical volumes in the volume group where /dev/dsk/c0t4d0 and /dev/dsk/c1t4d0 refer to the same physical volume (referenced via different controllers), and the volume group already contains /dev/dsk/c0t4d0. /dev/dsk/c0t4d0 remains the primary link (in use) and /dev/dsk/c1t4d0 becomes the alternate link.

vgextend  /dev/vg03 /dev/dsk/c1t4d0 

Add a spare physical volume to a volume group:

vgextend  -z y /dev/vg03 /dev/dsk/c2t4d0 

WARNINGS

The new physical volume which has been added to the volume group could potentially have a different block size compared to physical volumes already in the volume group.

If a logical volume is created on two or more physical volumes which have a different block size, it is not possible to use such logical volume for file system purposes (see extendfs(1M)).

For example, when a logical volume contains physical volumes that all have 1k block size, and then it is extended to contain a physical volume with 2k block size, then the block size of the volume group is increased to 2k.