vgchange(1M)vgchange(1M)NAMEvgchange - set LVM volume group availability
SYNOPSIS
Activate volume group
availability quorum]
resync_daemon_count] [vg_name...]
Set volume group high-availability cluster attributes
cluster sharable] vg_name
Change activation mode of sharable volume group
availability {vg_name...}
Quiesce an active volume group
quiesce_mode quiesce_time] vg_name
Resume a quiesced volume group
vg_name
Remarks
Serviceguard cluster operations require the installation of the
optional 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.
If a combination of volume groups version 1.0 and 2.0 or higher argu‐
ments are supplied, then the arguments may not be processed in the
order they are listed on the command line.
DESCRIPTION
The command with the option activates or deactivates one or more volume
groups.
For volume groups that are used in a high availability cluster, when
the option is specified together with the option, the command allows
cross-activation, changing the activation mode of an active sharable
volume group directly to the specified activation mode, without first
having to deactivate the volume group.
The command with the specifies whether the indicated volume group(s)
can be used in a high availability cluster, optionally the option can
also be specified to configure whether the volume group is sharable (or
is for exclusive activation only).
The command without the resync_daemon_count option (default) will spawn
one nomwcsyncd process for each volume group containing logical vol‐
umes, and this can degrade system performance when many of these volume
groups are activated at the same time. The resync_daemon_count option
provides a way to control the number of concurrent nomwcsyncd processes
spawned. This parameter is advisory, LVM may use a different value
internally as necessary.
The option allows quiescing an active volume group to facilitate creat‐
ing a consistent disk snapshot copy of all the physical volumes in the
volume group. Metadata on the physical volumes is brought current and
remains unchanged until normal operation is resumed using the option
(or when the optionally specified quiesce_time time has expired).
Specifying when quiescing the volume group quiesces application reads
and writes to the volume group. This mode is suitable for most situa‐
tions. Specifying when quiescing the volume group quiesces application
writes to the volume group while allowing reads to proceed as usual.
This mode provides improved access to the data when used with applica‐
tions that are capable of quiescing updates while allowing queries.
See the section for a more complete description of quiesced volume
groups.
vg_name must be defined as a volume group in the file or If vg_name is
omitted, all volume groups defined in and are affected, except when the
or options are specified. Only a single volume group can be provided
with these options.
High Availability Cluster Overview
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
software services are used to coordinate shared access to the same vol‐
ume 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 also
marked as sharable, it may be activated in shared mode for read-write
access by all the nodes in the cluster.
The configuration of a shared volume group can be changed only if it is
activated in exclusive mode. Cross-activation between shared and
exclusive modes of shared volume groups is possible with the option to
Simultaneously quiescing a volume group on all the systems sharing the
volume group can be accomplished by invoking with the option from any
node in the cluster. A Serviceguard cluster-lock volume group cannot
be quiesced, because initializing or updating the cluster-lock requires
writing to the disk.
Options and Arguments
recognizes the following options and arguments:
vg_name The path name of a volume group.
Set volume group availability.
availability can have one of the following
values:
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 option.
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; other‐
wise, the volume group is not acti‐
vated.
With the option, the activation mode of
a shared volume group is changed to
exclusive. The volume group will
remain active during the operation.
The operation will not be performed if
the volume group is active in more than
one node, or if it is not currently in
shared mode.
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 avail‐
ability cluster and marked sharable;
otherwise, the volume group is not
activated.
Please note HP MirrorDisk/UX software
is only supported in a clustered envi‐
ronment with a maximum of two nodes
configured for volume group version 1.0
and 2.0. For volume group version 2.1
or higher, HP MirrorDisk/UX software is
supported in a clustered environment
with a maximum of sixteen nodes config‐
ured.
With the option, the activation mode of
a shared volume group is changed to
shared. The volume group will remain
active during the operation. The oper‐
ation will only be performed if the
current activation mode of the volume
group is exclusive.
If the or option is executed on a currently
active volume group, without the option,
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 com‐
mand (see vgsync(1M)).
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.
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.
Control the membership of volume groups in a high availability
cluster.
cluster can have one of the following values:
Mark each specified volume group as a member
of a 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. may be optionally specified
with the option to indicate whether the
VG is sharable, and when the option is
used without the VG is marked not
sharable.
Remove each specified volume group from mem‐
bership in the high availability
cluster. The high availability soft‐
ware does not have to be running to
perform this operation.
The volume group must be deactivated with the
option before a option can be executed.
Force deactivation of each specified volume group
and its associated logical volumes while a
sync is in progress.
This option requires the deactivation option,
otherwise an error will be returned.
This option is only valid for high availabil‐
ity clusters.
Disable the opening of logical volumes that belong to each spec‐
ified volume group.
If the option is set, later attempts to open
the logical volumes will fail. To allow an
opening of these logical volumes to succeed,
execute
Activate each specified volume group only if all of the physical
volumes
that belong to it are available.
Set the quorum enforcement for each specified volume group.
quorum can have one of the following values:
Enforce the quorum requirement.
This is the default.
Ignore the quorum requirement.
The 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.
Disable the synchronization of stale physical extents
within the volume group specified by vg_name.
This option is only effective when used with
the or option.
Automatically resume normal read/write access to the volume
group
once the specified quiesce_time (in seconds)
has expired. This option should be used when
quiescing a volume group that contains criti‐
cal resources (e.g., root or swap logical vol‐
ume) that are necessary for normal operation
of the system, or other circumstances where
manually executing the may not be possible
once the volume group is quiesced. The qui‐
esce_time can be any value from 1 to 2^31-1.
This option is only valid when used with the
option.
Cross-activate a active sharable volume group, changing the
activation mode
to the specified activation mode. This option
is only valid when used with the availability
option. Cross-activation can only be used to
change the activation mode from shared mode to
exclusive mode, or from exclusive mode to
shared mode.
specify the advisory count to control the number of
nomwcsyncd threads spawned for processing when
activating the volume group(s). Specifying a
resync_daemon_count of causes a reasonable
number of threads to be spawned (currently
defined to be 4).
Quiesce an active volume group to guarantee that
the LVM metadata is consistent. This allows a
system administrator to perform a snapshot of
all the disks in the volume group. The volume
group remains quiesced until it is resumed
again using the option or automatically after
the optionally specified quiesce_time (given
using the option) has expired. See the sec‐
tion for a more complete description of qui‐
esced volume groups. The quiesce_mode can
have one of the following values:
Quiesce both reads and writes to the volume
group.
Quiesce writes to the volume group.
Applications may open and read from
logical volumes belonging to the volume
group.
Resume a previously quiesced volume group.
I/O that was quiesced is allowed to complete.
LVM commands and resync operations are
enabled. See the section for a more complete
description of quiesced volume groups.
Control the sharability of volume groups in a high availability
cluster.
sharable can have one of the following values:
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.
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
option before a option can be executed.
Activate each specified volume group using multiple parallel
threads.
Physical volumes will be attached to the vol‐
ume group using threads. If the option is not
specified with the option, logical volumes of
the volume group will also be synchronized
using threads. Activation will be serial
across volume groups and logical volumes
belonging to different volume groups will be
synchronized serially.
The maximum number of threads used can be con‐
trolled using the system tunable.
NOTE: With this option, the selection of pri‐
mary path and ordering of alternate links may
vary across volume group activations.
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 Consis‐
tency Recovery section of lvdisplay(1M)). In a non-shared environment,
LVM supports and the recovery. Logical volumes in 1.0 and 2.0 volume
group versions, activated in shared mode, do not support for mirror
consistency recovery.
Recover mirror consistency
by using the Mirror Write Cache and Mirror Consistency
Record. This mode implies that the Mirror Write Cache
is on.
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.
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 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
option appears on the command line.
General Activation
If cannot access a physical volume, it lists the volume's status as
missing. If too many physical volumes in the volume group are missing,
reports that the group does not have a quorum and cannot be activated.
The lack of a quorum can be overridden with the 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 deacti‐
vated. They remain unchanged until the command is issued to
resume access to the VG or until the optionally specified
quiesce_time has expired.
· When is specified, reads and writes are queued until the vol‐
ume group is resumed. When 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
determines the language in which messages are displayed.
If 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
Deactivate volume group
Forced deactivation of volume group
Activate volume group using multiple parallel threads:
Activate volume group without synchronizing extents that are not cur‐
rent on logical volumes that have Mirror Write Cache turned on:
Exclusive Activation
Set up volume group for use in a high availability cluster:
Activate all volume groups; activate those that are marked for member‐
ship in a high availability cluster in shared mode:
Activate all volumes that are marked for membership in a high avail‐
ability cluster in exclusive mode:
Cross Activation
Set up volume group for use in a high availability cluster.
To make configuration changes, to a volume group activated in shared
mode, deactivate the volume group by executing the following command on
each cluster node except one:
On the single node, where the volume group is active:
Quiescing a Volume Group
Quiesce LVM metadata writes and application reads and writes to volume
group
Quiesce LVM metadata and application writes but allow application reads
to volume group
Resume normal reads and writes to volume group (after having quiesced
them earlier) :
Quiesce volume group quiescing both reads and writes and automatically
resume normal read/write access in 600 seconds:
WARNINGS
Ordinary Operation
In ordinary operation (that is, 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
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 dur‐
ing 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 sys‐
tems it is recommended that logical volumes be accessed only by one
system at a time. If logical volumes must 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 ALSOmount(1M), vgcreate(1M), vgdisplay(1M), vgextend(1M), vgreduce(1M).
If Serviceguard is installed: cmcheckconf(1M), cmquerycl(1M), and
vgchange(1M)
