HP-UX Reference (11i v3 07/02) - 1M System Administration Commands N-Z (vol 4)

v
vgchange(1M) vgchange(1M)
Volume Groups section for a more complete description of quiesced volume groups.
-S sharable Control the sharability of volume groups in a high availability cluster. sharable
can have one of the following values:
y Mark each specified volume group as sharable. The high availability software
must be running; otherwise, the volume group is not marked. This only has
to be done from one node of the cluster.
n Remove the shared attribute from the volume group. The high availability
software does not have to be running to perform this operation.
The volume group must be deactivated with the
-a n option before a -S yn
option can be executed.
Mirrored Disk Activation
When the optional HP MirrorDisk/UX software is running and a volume group is activated, LVM performs
the necessary mirror consistency recovery for each logical volume in the volume group based on the state of
Mirror Write Cache and Mirror Consistency Recovery (see the Consistency Recovery section of
lvdisplay(1M)). In a non-shared environment, LVM supports MWC, NOMWC and the NONE recovery. But in
shared environment, LVM only supports
NOMWC and the NONE recovery.
MWC Recover mirror consistency by using the Mirror Write Cache and Mirror Consistency
Record. This mode implies that the Mirror Write Cache is on.
NOMWC Recover mirror consistency by searching all logical extents and copying data from a non-
stale copy to all the other mirror copies. This mode implies that the Mirror Write Cache is
off.
NONE Do not recover mirror consistency during volume group activation on this logical volume
following a system crash. This mode implies that the Mirror Write Cache is off.
Once mirror consistency is recovered using the configured policy, the mirrors are resynchronized (any stale
extents made current) by copying data from a non-stale copy to the stale mirror copies. If the
-s option is
specified on the command line, mirror synchronization does not occur. However, for those logical volumes
that have Mirror Write Cache turned off, mirror synchronization is done independently of whether the
-s
option appears on the command line.
General Activation
If vgchange cannot access a physical volume, it lists the volumes status as missing. If too many physical
volumes in the volume group are missing, vgchange reports that the group does not have a quorum and
cannot be activated. The lack of a quorum can be overridden with the -q n option.
Quiesced Volume Groups
A quiesced volume group presents a stable and consistent disk image suitable for creating snapshot copies
of the disks in the volume group.
Quiesced volume groups have the following characteristics:
The physical volumes in the volume group appear as though the logical volumes were closed and
the volume group was deactivated. They remain unchanged until the
vgchange -R command is
issued to resume access to the VG or until the optionally specified quiesce_time has expired.
When -Q rw is specified, reads and writes are queued until the volume group is resumed. When
-Q w is specified, reads proceed as usual, but writes are queued until the volume group is
resumed. In the latter case, reading from the volume group will return the last data written
before the volume group was quiesced.
LVM display commands are allowed to proceed as usual.
LVM mirror resynchronization and configuration commands are rejected.
I/O that is queued because a volume group is quiesced will not be completed until after the volume
group is resumed, regardless of any logical volume I/O timeout that is set on the LVs. Some appli-
cations may be sensitive to this delay and could report errors or warnings as a result.
HP-UX 11i Version 3: February 2007 4 Hewlett-Packard Company 621