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Shared Volume Group Considerations

Volume group version 2.2 and higher with snapshot logical volumes conﬁgured cannot be actived in

shared mode. See lvm(7) for information on snapshot volumes.

Mirrored Disk Activation

When the optional HP MirrorDisk/UX software is running and a volume group is activated, LVM per-

forms 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. Logi-

cal volumes in 1.0 and 2.0 volume group versions, activated in shared mode, do not support

MWC for mir-

ror consistency 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 logi-

cal 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

vgchange cannot access a physical volume, it lists the volume’s status as missing. If too many physi-

cal 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 applications may be sensitive to this delay and could report errors or warnings as a result.

EXTERNAL INFLUENCES

Environment Variables

LANG determines the language in which messages are displayed.

LANG is not speciﬁed or is null, it defaults to "C" (see lang (5)).

If any internationalization variable contains an invalid setting, all internationalization variables default

to "C" (see environ (5)).

EXAMPLES

Activate volume group /dev/vg03:

vgchange -a y /dev/vg03

HP-UX 11i Version 3: October 2010 − 5 − Hewlett-Packard Company 5