pvchange(1M) pvchange(1M)
NAME
pvchange - change characteristics and access path of a physical volume in an LVM volume group
SYNOPSIS
autobackup] availability pv_path
autobackup] pv_path
autobackup] autoswitch pv_path
autobackup] extensibility pv_path
autobackup] IO_timeout pv_path
autobackup] sparepv pv_path
autobackup] proactivepolling pv_path
Remarks
Only can be performed if the volume group is activated in shared mode. All other options are not allowed for physical volumes in shared
volume groups.
DESCRIPTION
The command changes the characteristics and access path of a physical volume (pv_path) in a volume group.
For multiported devices accessed through multiple paths, you can use to customize the following behaviors:
o How LVM switches from one path to another in case of path failure or recovery.
o How LVM tests alternate links.
also permits you to switch manually to a specific path to the physical volume.
sets the allocation permission to add physical extents to the physical volume.
If you have installed the optional HP MirrorDisk/UX software, you can use the option to designate a spare physical volume to be used to
replace an existing physical volume within a volume group when mirroring is in effect, in the event the existing physical volume fails.
can also be used to attach or detach specific paths or physical volumes (see WARNINGS section).
Options and Arguments
recognizes the following options and arguments.
pv_path The block device path name of a physical volume.
Set automatic backup for this invocation of this command.
autobackup can have one of the following values:
Automatically back up configuration changes made to the logical volume.
This is the default.
After this command executes, the command (see vgcfgbackup(1M)) is executed for the volume group to which
the logical volume belongs.
Do not back up configuration changes this time.
Attach or detach the physical volume
pv_path. availability can have one of the following values:
Attach the indicated path to the physical volume.
An attached path or device is available for LVM to use. Attaching a path makes that path available to
the volume group, if possible. LVM may begin using the path if necessary to access the disk. If for-
merly all the paths were unavailable to a given physical volume, making any path available will make the
physical volume available again.
(See WARNINGS section). Detach only the indicated path to the physical volume. A detached path is not avail-
able for LVM to use. Detaching a single path causes LVM to close the device for that one path and to
stop using it. If the path is the primary path to the device, LVM will begin using the best alternate
path to the device that is available. When the only path to a device is detached, the associated physi-
cal volume will be unavailable to the volume group. The path remains part of the volume group but no I/O
is queued to it and the path will remain unused by LVM until it is reattached. LVM will only stop using
the physical volume when all the paths to the physical volume are detached. Individually detaching all
the paths to a physical volume has the same consequences as detaching the physical volume entirely using
the option. The system administrator may safely diagnose or replace hardware along the path detached,
but care should be taken to avoid accessing the physical volume if it is still being accessed by LVM via
other active paths to it.
Detach the given path and all other paths to the physical volume.
The system administrator should always presume that all the disks that belong to an active volume group
are attached and may be used by LVM at any time, unless LVM has been specifically notified to detach
them. Prior to replacing or repairing any disk belonging to an active volume group, the administrator
must first detach the physical volume using this command.
When a physical volume is detached, LVM closes all the paths to the physical volume and no longer directs
any I/O operations to it. If a suitable spare physical volume is available in the volume group, LVM will
use it to reconstruct the detached disk. The given path must be an attached path to the physical volume;
otherwise, the command will fail and display an error message indicating the problem.
If for any reason the use of the option fails, the physical volume can still be detached from the volume
group by individually detaching each of the paths to the physical volume using the option instead.
(See WARNINGS section). Immediately begin accessing the associated physical volume named by pv_path.
(See WARNINGS section). This option specifies the autoswitch behavior for multiported physical volumes accessed
through multiple paths. It has no effect for physical volumes without alternate paths. autoswitch can have one
of the following values:
LVM is directed to automatically switch from the path it is using whenever a
better path to the physical volume is available. LVM will switch paths when a better path recovers
(after it had failed earlier), or if the current path fails and another path is available. This is the
default.
LVM is directed to automatically switch to using the best available path only
when the path currently in use is unavailable. LVM will continue using a specific path for the physical
volume as long as it works, regardless of whether another better path recovers from a failure.
Set the allocation permission to add physical extents to the physical volume
pv_path. extensibility can have one of the following values:
Allow allocation of additional physical extents on the physical volume.
This is the default.
Prohibit allocation of additional physical extents on the physical volume.
However, logical volumes residing on the physical volume are accessible.
Set the I/O timeout value for the physical volume, to the number of
seconds indicated. An I/O timeout value of zero(0) causes the system to use the default value supplied by the
device driver associated with the physical device. I/O timeout value is used by the device driver to determine
how long to wait for disk transactions to complete before concluding that an I/O request can not be completed
(and the device is offline or unavailable).
This option is only applicable for physical volumes belonging
to volume groups version 1.0. Sparing is not supported for physical volumes belonging to volume groups version
2.0 or higher. This option requires the installation of the optional HP MirrorDisk/UX software.
This option allows you to change the physical volume specified by pv_path into a spare physical volume for its
volume group, or change the specified spare physical volume back into a regular physical volume for this volume
group. No physical extents from a spare physical volume will be available as part of the "free" pool of extents
in the volume group. A spare physical volume will only be used in the event that another physical volume within
this volume group becomes unavailable (fails). sparepv can have one of the following values:
Change the specified physical volume to be a "stand-by" spare for its
volume group. The specified physical volume must not have extents allocated on it (i.e., no logical vol-
umes residing on it) at the time this command is issued. A stand-by spare physical volume will only be
used in the event of a failure of another physical volume -- prior to such a failure, no logical volume
is allowed to reside on it.
Change the specified spare physical volume back into a regular physical volume.
If the physical volume was a stand-by spare, then all of the disk space associated with it will be imme-
diately available for use by logical volumes. If the physical volume is an "active" spare, that is, it
was previously a stand-by spare but then took over for a failed physical volume, it will simply mark the
physical volume as a regular member of its volume group and the logical volumes residing on it will
remain unchanged.
(See section). This option specifies LVM's proactive polling behavior on alternate links. proactivepolling can have
one of the following values:
Enable LVM's proactive polling for alternate links of a physical volume.
LVM will periodically test alternate links. This is the default.
Disable LVM's proactive polling for alternate links of a physical volume.
LVM will not periodically test alternate links.
Attaching and Detaching Physical Volumes
Detaching a physical volume makes the data on that disk unavailable. LVM will not write or read any user data or LVM metadata to the disk
while it is detached. Consequently, it is important for the administrator to ensure that the data on the disk is sufficiently mirrored to
satisfy availability requirements prior to making the device unavailable by detaching it.
Although detaching a path or physical volume ensures it is unavailable to LVM, attaching a path or physical volume will not necessarily
make the path or physical volume available again. Attaching a path or physical volume only makes it available for LVM to use once the disk
is working. For instance, if a disk is spinning up, LVM will successfully attach the disk, but the disk will not be available until it is
ready.
Detaching a physical volume or path only temporarily changes the status of the indicated path or physical volume. However, it does not
change the volume group configuration. When a physical volume is detached, it will automatically be attached again the next time the vol-
ume group is activated using the command (see vgchange(1M)). If the objective is to permanently add or remove a path or physical volume
from the volume group, the or commands (see vgextend(1M), and vgreduce(1M)) should instead be used.
Warning: Detaching any physical volume or path using the or options also disables automatically attaching any paths to any of the physical
volumes in the volume group. LVM will no longer attempt to automatically recover any unattached physical volumes in the volume group, not
just the ones explicitly detached. To cause LVM to once again automatically attach devices in the volume group use the options of command.
Attaching or Detaching Physical Volumes in Shared Volume Groups
The scope of the command is limited to the specific node on which it runs. Systems that are part of a Serviceguard cluster operate inde-
pendently. To replace disks that are part of a volume group shared by a Serviceguard cluster, the physical volume must be detached and
attached independently on each of the systems in the cluster.
Alternate Links (PVLINKS)
In this release of HP-UX, LVM continues to support Alternate Links to a device to allow continued access to the device, if the primary link
fails. This multiple link or multipath solution increases data availability, but does not allow the multiple paths to be used simultane-
ously.
There is a new feature introduced in the Mass Storage Subsystem on this version of HP-UX that also supports multiple paths to a device and
allows access to the multiple paths simultaneously. The Mass Storage Subsystem will balance the I/O load across the valid paths. This new
multi-path behavior is enabled and disabled through the use of the command. See scsimgr(1M) for details.
It is no longer required or recommended to configure LVM with alternate links. However, it is possible to maintain the traditional LVM
behavior. To do so, both of the following criteria must be met:
o Only the legacy device special file naming convention is used in the volume group configuration.
o The command is used to disable the Mass Storage Subsystem multipath behavior.
EXTERNAL INFLUENCES
Environment Variables
determines the language in which messages are displayed.
If is not specified or is null, it defaults to (see lang(5)).
If any internationalization variable contains an invalid setting, all internationalization variables default to (see environ(5)).
EXAMPLES
Prohibit the allocation of additional physical extents to a physical volume:
Allow the allocation of additional physical extents to a physical volume:
Only switch paths when the current path is unavailable. Do not switch back to a prior path which had failed and has recovered, when the
current path works:
Switch paths whenever a better path becomes available again after a failure, even if the current path is fine:
Manually switch a physical volume to use another controller path:
Set the IO_timeout value for a physical volume to 60 seconds:
Set the IO_timeout value for a physical volume to zero(0) to use the driver default:
Change the (empty) physical volume to become a stand-by spare for the volume group:
Change the (active or stand-by) spare physical volume to become a regular member of the volume group:
Enable LVM's proactive polling of alternate links
Disable LVM's proactive polling of alternate links
Detach a path to a physical volume
Detach all the paths to a physical volume
Attach a path to a physical volume
The command may be used to attach all the physical volumes in the volume group and resume, automatically attaching the failed physical vol-
umes.
WARNINGS
If the Mass Storage Subsystem multipath solution is enabled, the command options that are link specific may not stop I/Os or switch links,
as they did in earlier releases. This means that and may not stop all I/Os on a given path. The command should be used to disable the
links.
When the proactive polling is enabled, LVM will not be testing alternate links unless legacy mode is in operation, even if legacy paths are
being used.
SEE ALSO
pvdisplay(1M), scsimgr(1M), vgcfgbackup(1M), vgchange(1M). vgextend(1M), vgreduce(1M), environ(5), lang(5), intro(7), lvm(7).
pvchange(1M)