HP-UX System Administrator's Guide: Logical Volume Management (5900-3028, March 2013)

--- Logical volumes ---
LV Name /dev/vg1/lvol1
LV Status available/syncd
LV Size (Mbytes) 204784
Current LE 25598
Allocated PE 51196
Used PV 2
--- Physical volumes ---
PV Name /dev/disk/disk46
PV Status available
Total PE 38396
Free PE 12798
...
PV Name /dev/disk/disk47
PV Status available
Total PE 38396
Free PE 12798
Quiescing and Resuming a Volume Group
If you plan to use a disk management utility to create a backup image or “snapshot” of all the
disks in a volume group, you must make sure that LVM is not writing to any of the disks when the
snapshot is being taken; otherwise, some disks can contain partially written or inconsistent LVM
metadata. To keep the volume group disk image in a consistent state, you must either deactivate
the volume group or quiesce it.
Deactivating the volume group requires you to close all the logical volumes in the volume group,
which can be disruptive. For example, you must unmount any file system using a logical volume
in the volume group. However, temporarily quiescing the volume group enables you to keep the
volume group activated and the logical volumes open during the snapshot operation, minimizing
the impact to your system.
You can quiesce both read and write operations to the volume group, or just write operations.
While a volume group is quiesced, the vgdisplay command reports the volume group access
mode as quiesced. The indicated I/O operations queue until the volume group is resumed, and
commands that modify the volume group configuration fail immediately.
NOTE: Individual physical volumes or logical volumes cannot be quiesced using this feature. To
temporarily quiesce a physical volume to disable or replace it, see “Disabling a Path to a Physical
Volume” (page 86). To quiesce a logical volume, quiesce or deactivate the volume group. To
provide a stable image of a logical volume without deactivating the volume group, mirror the
logical volume, then split off one of the mirrors, as described in “Backing Up a Mirrored Logical
Volume” (page 68).
Quiescing a volume group is not persistent across reboots.
To quiesce a volume group, use the vgchange command with the -Q option as follows:
# vgchange -Q mode vgnn
The mode parameter can be either rw, which blocks both read and write operations, or w, which
permits read operations but blocks write operations.
By default, the volume group remains quiesced until it is explicitly resumed. You can specify a
maximum quiesce time in seconds using the -t option. If the quiesce time expires, the volume
group is resumed automatically. For example, to quiesce volume group vg08 for a maximum of
ten minutes (600 seconds) but permitting read operations, enter the following command:
# vgchange -Q w -t 600 vg08
To resume a quiesced volume group, use the vgchange command with the -R option as follows:
# vgchange -R vgnn
Common LVM Tasks 65