vgchange(1M) vgchange(1M)
NAME [Toc] [Back]
vgchange - set LVM volume group availability
SYNOPSIS [Toc] [Back]
Activate volume group
/usr/sbin/vgchange -a availability [-l] [-p] [-q quorum] [-s] [-P
resync_daemon_count] [vg_name...]
Assign to high availability cluster and mark volume group sharable [Toc] [Back]
/usr/sbin/vgchange -c cluster -S sharable vg_name
Remarks [Toc] [Back]
MC/ServiceGuard cluster operations require the installation of the
optional MC/ServiceGuard software, which is not included in the
standard HP-UX operating system.
Mirrored disk operations require the installation of the optional HP
MirrorDisk/UX software, which is not included in the standard HP-UX
operating system.
DESCRIPTION [Toc] [Back]
The vgchange command with the -a option activates or deactivates one
or more volume groups.
The vgchange command with the -c option controls the membership of one
or more volume groups in a high availability cluster. The vgchange
command with the -c and -S options control the membership of a volume
group and mark it sharable.
The vgchange command without the -P resync_daemon_count option
(default) will spawn one nomwcsyncd process for each NOMWC/NONE volume
group being activated. This may create a lot of nomwcsyncd processes
running concurrently when it activates a large number of NOMWC/NONE
volume groups and overload.
The -P resync_daemon_count option provides a way to control the number
of concurrent nomwcsyncd processes. The count is an advisory number
and a different count might be chosen internally if load balance or
other reason is needed. When specified, there are up to
resync_daemon_count + 1 nomwcsyncd processes; one of them is the
controlling processing to spawn others. -P 0 will use the system
default (currently defined to be 4).
vg_name must be defined as a volume group in the file /etc/lvmtab. If
vg_name is omitted, all volume groups defined in /etc/lvmtab are
affected.
High Availability Cluster Overview [Toc] [Back]
Volume groups can be defined on disk volumes that are accessible by
more than one system in a high availability cluster. This situation
has a high potential for data corruption unless higher level cluster
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software services are used to coordinate shared access to the same
volume group by all systems.
A volume group can be marked as part of a cluster. When such a group
is activated in exclusive mode, it can be accessed for exclusive
read-write activity by only one of the systems at a time; the other
systems can have read-only access to the data. When the volume group
is marked as sharable, it may be activated in shared mode for readwrite
access by all the nodes in the cluster.
Options and Arguments [Toc] [Back]
vgchange recognizes the following options and arguments:
vg_name The path name of a volume group.
-a availability Set volume group availability. availability
can have one of the following values:
y Activate each specified volume
group and all associated physical
and logical volumes for read-write
access. If a volume group is
marked as part of a high
availability cluster, it is
activated in exclusive read-write
mode, as for the -a e option.
e Activate each specified volume
group and all associated physical
and logical volumes for exclusive
read-write access. The volume
group must be marked as part of a
high availability cluster, and the
availability software must be
running on the system; otherwise,
the volume group is not activated.
s Activate each specified volume
group and all associated physical
and logical volume for shared
read-write access. The volume
group must be marked as part of a
high availability cluster and
marked sharable; otherwise, the
volume group is not activated.
If any of the logical volumes in
the volume group are mirrored, and
if there are more than two systems
in the high availability cluster,
this volume group will not be
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activated because HP MirrorDisk/UX
software is only supported in a
clustered environment with a
maximum of two nodes configured.
If the -a y or -a e option is executed
on a currently active volume group,
vgchange attempts to include any
physical volumes that were previously
listed as missing. This is useful if a
physical volume has come back online.
However, no automatic synchronization of
any mirrored logical volumes is done.
If synchronization is required, execute
the vgsync command (see vgsync(1M)).
r Activate each specified volume
group and all associated physical
and logical volumes for read-only
access. This option is ignored for
a volume group that is already
activated.
If a volume group is marked as part
of a high availability cluster, the
high availability software must be
running on the system; otherwise,
the volume group is not activated.
n Deactivate each specified volume
group and its associated logical
volumes. You must close the
logical volumes prior to executing
this option. For example, if the
logical volume contains a file
system, the file system must be
unmounted.
-c cluster Control the membership of volume groups in a
high availability cluster. cluster can have
one of the following values:
y Mark each specified volume group as
a member of the high availability
cluster. The high availability
software must be running;
otherwise, the volume group is not
marked. Needs to be done on one
node only.
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n Remove each specified volume group
from membership in the high
availability cluster. The high
availability software does not need
to be running.
The volume group must be deactivated with the
-a n option before a -c y|n option can be
executed.
-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. Needs to be done on one
node only.
n Remove the shared attribute from
the volume group. The high
availability software does not need
to be running.
The volume group must be deactivated with the
-a n option before a -S y|n option can be
executed.
-l Disable the opening of logical volumes that
belong to each specified volume group. If
the -l option is set, later attempts to open
the logical volumes will fail. To allow an
opening of these logical volumes to succeed,
execute lvchange -a y.
-p Activate each specified volume group only if
all of the physical volumes that belong to it
are available.
-q quorum Set the quorum enforcement for each specified
volume group. quorum can have one of the
following values:
y Enforce the quorum requirement.
This is the default.
n Ignore the quorum requirement.
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The -q n option can be used to activate the
volume group when the disk quorum is not
maintained because too many disks were lost.
Since it ensures the integrity of the LVM
configuration information, it is normally not
advisable to override the quorum.
-s Disable the synchronization of stale physical
extents within the volume group specified by
vg_name. This option is only effective when
used with the -a y or -a e option.
-P resync_daemon_count
gives the advisory count to control the
number of nomwcsyncd processes on volume
group activation.
Mirrored Disk Activation [Toc] [Back]
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 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. This mode implies
that the Mirror Write Cache is off.
Next, mirror synchronization refreshes stale mirror copies by copying
data from a nonstale copy. 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 [Toc] [Back]
If vgchange cannot access a physical volume, it lists the volume's
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
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the -q n option.
EXTERNAL INFLUENCES [Toc] [Back]
Environment Variables
LANG determines the language in which messages are displayed.
If 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 [Toc] [Back]
Activate volume group /dev/vg03:
vgchange -a y /dev/vg03
Deactivate volume group /dev/vg03:
vgchange -a n /dev/vg03
Activate volume group /dev/vg03 without synchronizing extents that are
not current on logical volumes that have Mirror Write Cache turned on:
vgchange -a y -s /dev/vg03
Exclusive Activation [Toc] [Back]
Set up volume group /dev/vg03 for use in a high availability cluster:
vgchange -a n /dev/vg03 # Deactivate volume group
vgchange -c y /dev/vg03 # Enable volume group for HA cluster
vgchange -c y -S y /dev/vg03 # Enable volume group for HA cluster
and mark as sharable
vgchange -a e /dev/vg03 # Activate volume group in exclusive mode
vgchange -a s /dev/vg03 # Activate volume group in shared mode
Activate all volume groups; activate those that are marked for
membership in a high availability cluster in exclusive mode:
vgchange -a y
Activate all volumes that are marked for membership in a high
availability cluster in exclusive mode:
vgchange -a e
WARNINGS [Toc] [Back]
Ordinary Operation
In ordinary operation (i.e., without the optional high availability
software), it is possible to activate a volume group for read-write
access from more than one physically connected system, leading to a
high potential for data corruption. Therefore, if access is desired
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from more than one system to a single volume group, it is important
that only one system activate the volume group for read-write access;
the other systems can use read-only access. There is no problem if
all systems activate the volume group for read-only access.
Furthermore, volume group information is only read from the disks
during volume group activation. Dynamic changes to the volume group
such as the following are not propagated to other systems sharing the
volume group:
Logical volume configuration changes.
Changes to the status of the mirrored extents.
Bad-block relocation that occurs during write operations.
Because of these limitations, when sharing volume groups between
systems it is recommended that logical volumes be accessed only by one
system at a time. If logical volumes need to be accessed
simultaneously, the logical volumes should not be mirrored and should
not have bad-block relocation turned on, or all systems should use
read-only access to the logical volumes.
SEE ALSO [Toc] [Back]
mount(1M), vgcreate(1M), vgextend(1M), vgreduce(1M), vgdisplay(1M).
If MC/ServiceGuard is installed: cmcheckconf(1M), cmquerycl(1M), and
Managing MC/ServiceGuard.
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