HP-UX System Administrator's Guide: Logical Volume Management (762803-001, March 2014)

When you configure non-root logical volume as a swap or dump, ensure that AUTO_VG_ACTIVATE
settings in /etc/lvmrc is turned on:
# grep "AUTO_VG_ACTIVATE=" /etc/lvmrc
AUTO_VG_ACTIVATE=1
Without this setting, the logical volumes from non-root VG will not be configured as a swap/dump
device after the reboot since the corresponding volume group stays deactivated.
NOTE: Root volume group gets activated on every reboot regardless of AUTO_VG_ACTIVATE
settings.
In MMB (Maintenance Mode Boot) mode of booting, the logical volumes from non-root VG will
not be configured automatically as swap/dump regardless of AUTO_VG_ACTIVATE settings and
entries in fstab file. This is because MMB is a special mode of boot that does not activate any
VG. Once the system is booted into MMB, you can perform the following steps to configure your
non-root logical volume as swap or dump:
1. Activate the volume group that hosts the non-root logical volume:
Example:
# vgchange –a y /dev/vgsys
2. Add the non-root logical volume as dump or swap using crashconf command
Example:
# swapon /dev/vgsys/lvol1
# crashconf /dev/vgsys/lvol1
NOTE: Primary swap and dump configured through lvlnboot(1M) command (on logical
volumes from root VG) will be configured automatically even in MMB mode of boot.
3.11 Creating and Administering Snapshot Logical Volumes
Beginning with the HP-UX 11i v3 March 2010 Update, LVM provides the ability to create snapshot
logical volumes. A snapshot represents a point-in-time image of a logical volume. LVM snapshots
let you:
• Use snapshots to back up data on the logical volume without splitting the logical volume. This
reduces the space requirement.
• Create snapshots faster than manually copying over multiple point-in-time copies of the logical
volume.
• Create multiple snapshots of a logical volume. This enables you to have images of the logical
volume for multiple point in time without allocating space equivalent to the entire size of the
logical volume per copy.
Up to 255 snapshots can be created off a single logical volume. The logical volume (referred to
as the original logical volume) and all of its snapshots together form a snapshot tree and maintains
a successor/predecessor relationship with each other.
When created, a snapshot shares all its data with that of the original logical volume. The snapshot
gets a copy of its own data only when a write occurs (copy before write) onto itself or its successor.
This process is called data unsharing. The smallest unit for data unsharing is the volume group's
unshare unit, specified by the vgcreate -U option. See vgcreate(1M) for details.
Snapshots are by default read-only, but the user can choose to create writable snapshots. See
lvcreate(1M) and lvchange(1M) for more details.
For more information about snapshot logical volumes and snapshot trees, see the lvm(7) manpage
and the LVM Snapshot Logical Volumes white paper.
108 Administering LVM