HP-UX Reference (11i v2 07/12) - 7 Device (Special) Files, 9 General Information, Index (vol 10)

l
lvm(7) lvm(7)
NAME
lvm - Logical Volume Manager (LVM)
DESCRIPTION
The Logical Volume Manager (LVM) is a subsystem for managing disk space. The HP LVM subsystem
offers value-added features, such as mirroring (with the optional HP MirrorDisk/UX software), high availa-
bility (with the optional HP ServiceGuard software), and striping, that enhance availability and perfor-
mance.
Unlike earlier arrangements where disks were divided into fixed-sized sections, LVM allows the user to
consider the disks, also known as physical volumes, as a pool (or volume) of data storage, consisting of
equal-sized extents. The default size of an extent is 4 MB.
An LVM system consists of arbitrary groupings of physical volumes, organized into volume groups.A
volume group can consist of one or more physical volumes. There can be more than one volume group in
the system. Once created, the volume group, and not the disk, is the basic unit of data storage. Thus,
whereas earlier one would move disks from one system to another, with LVM, one would move a volume
group from one system to another. For this reason it is often convenient to have multiple volume groups on
asystem.
Volume groups can be subdivided into virtual disks, called logical volumes. A logical volume can span a
number of physical volumes or represent only a portion of one physical volume. The pool of disk space that
is represented by a volume group can be apportioned into logical volumes of various sizes. The size of a log-
ical volume is determined by its number of extents. Once created, logical volumes can be treated just like
disk partitions. Logical volumes can be assigned to file systems, used as swap or dump devices, or used for
raw access.
Commands
LVM information can be created, displayed, and manipulated with the following commands:
lvchange Change logical volume characteristics
lvcreate Stripe, create logical volume in volume group
lvdisplay Display information about logical volumes
lvextend Increase space, increase mirrors for logical volume
lvlnboot Prepare logical volume to be root, primary swap, or dump volume
lvmmigrate Prepare root file system for migration from partitions to logical volumes
lvreduce Decrease number of physical extents allocated to logical volume
lvremove Remove one or more logical volumes from volume group
lvrmboot Remove logical volume link to root, primary swap, or dump volume
pvchange Change characteristics of physical volume in volume group
pvcreate Create physical volume for use in volume group
pvdisplay Display information about physical volumes within volume group
pvmove Move allocated physical extents from one physical volume to other physical
volumes
vgcfgbackup Create or update volume group configuration backup file
vgcfgrestore Display or restore volume group configuration from backup file
vgchange Set volume group availability
vgcreate Create volume group
vgdisplay Display information about volume groups
vgexport Export a volume group and its associated logical volumes
vgextend Extend a volume group by adding physical volumes
vgimport Import a volume group onto the system
vgreduce Remove physical volumes from a volume group
vgremove Remove volume group definition from the system
vgscan Scan physical volumes for volume groups
The following commands are also available if the HP MirrorDisk/UX software is installed:
lvmerge Merge two logical volumes into one logical volume
lvsplit Split mirrored logical volume into two logical volumes
lvsync Synchronize stale mirrors in logical volumes
vgsync Synchronize stale logical volume mirrors in volume groups
HP-UX 11i Version 2: December 2007 Update − 1 − Hewlett-Packard Company 83