LVM Volume Group Dynamic LUN Expansion (DLE) and Contraction (DLC) (September 2009)

Introduction

LVM and MirrorDisk/UX now support the following volume groups:

• Version 1.0 — Supported on all current and previous versions of HP-UX 11i.

• Version 2.x — Version 2.0 volume groups are supported starting with the HP-UX 11i v3

March 2008 Update. Version 2.1 volume groups are supported starting with the HP-UX 11i

v3 September 2008 Update.

The vgmodify command is supported on Version 1.0 and Version 2.x volume groups. Version 2.x

support is provided starting with the HP-UX 11i v3 March 2009 Update.

For further details on the newly supported volume group versions, see the LVM Version 2.0 Volume

Groups in HP-UX 11i v3

white paper.

Overview

What can vgmodify do for me?

The new vgmodify command enables you to alter some characteristics of an existing volume group

(VG) or physical volume (PV) that were set with vgcreate or pvcreate. The modifiable attributes

for Version 1.0 volume groups are the maximum number of PVs, the maximum number of Logical

Volumes (LVs), the maximum number of extents per PV allowed in the VG, and whether a PV is to be

bootable or not. The modifiable attribute for Version 2.x volume groups is the maximum size of the

volume group. The vgmodify command handles the expansion (DLE) and contraction (DLC) of a LUN

for both Versions 1.0 and 2.x.

Before the introduction of vgmodify, all these operations required the data in the volume group to

be backed up and the volume group destroyed, or physical volume removed, before rebuilding and

reloading the data.

You can use the vgmodify command in two modes:

• Offline vgmodify when the volume group is deactivated (supported for Version 1.0).

Enables you to change the characteristics of a volume group, and handles expansion and

contraction (added in the HP-UX 11i v3 March 2009 Update) of a LUN.

• Online vgmodify when the volume group is active (supported for Versions 1.0 and 2.x).

Introduced in the HP-UX 11i v3 September 2008 Update, online vgmodify handles LUN

expansion for Version 1.0 volume groups.

For the HP-UX 11i v3 March 2009 Update, online vgmodify enables you to change the

characteristics of a volume group (Version 1.0 and 2.x volume groups), and handles

expansion (Version 2.x volume groups) and contraction (Version 1.0 and 2.x volume groups)

of a LUN.

When would I want to use vgmodify?

For Version 1.0 volume groups, use vgmodify to do the following tasks:

• Add more physical volumes than the max PV setting currently allows.

• Take account of a size change to a physical volume that was initialized via pvcreate.

• Make full use of the space available on a disk that is larger than the current maximum

number of physical extents per physical volume allows.

• Make full use of the space available on a disk that is larger than the current configuration.

• Contract a physical volume to a size smaller than the current configuration.