pvchange(1M)

NAME

pvchange — change characteristics and access path of physical volume in LVM volume group

SYNOPSIS

/usr/sbin/pvchange [-A autobackup] -a availability pv_path

/usr/sbin/pvchange [-A autobackup] -s pv_path

/usr/sbin/pvchange [-A autobackup] -S autoswitch pv_path

/usr/sbin/pvchange [-A autobackup] -x extensibility pv_path

/usr/sbin/pvchange [-A autobackup] -t IO_timeout pv_path

/usr/sbin/pvchange [-A autobackup] -z sparepv pv_path

Remarks

Only pvchange -a 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 pvchange command changes the characteristics and access path of a physical volume (pv_path) in a volume group.

For multiported devices accessed via multiple paths, pvchange may be used to customize the circumstances that may cause LVM to automatically switch from one path to another, or when LVM will switch back to a prior path which failed when it is available again (generally described as the physical volume's autoswitch behavior). pvchange also permits you to switch manually to a specific path to the physical volume (see WARNINGS section).

pvchange 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 -z 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.

pvchange can also be used to attach or detach specific paths or physical volumes (see WARNINGS section).

Options and Arguments

pvchange recognizes the following options and arguments.

pv_path

The block device path name of a physical volume.

-A autobackup

Set automatic backup for this invocation of this command. autobackup can have one of the following values:

y

Automatically back up configuration changes made to the logical volume. This is the default.

After this command executes, the vgcfgbackup command (see vgcfgbackup(1M)) is executed for the volume group to which the logical volume belongs.

n

Do not back up configuration changes this time.

-a availability

Attach or detach the physical volume pv_path. availability can have the following values:

y

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 formerly all the paths were unavailable to a given physical volume, making any path available will make the physical volume available again.

n

(See WARNINGS section). Detach only the indicated path to the physical volume. A detached path is not available 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 physical 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 -a N 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.

N

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 -a N 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 -a n option instead.

-s

(See WARNINGS section). Immediately begin accessing the associated physical volume named by pv_path.

-S autoswitch

(See WARNINGS section). This option specifies the autoswitch behavior for multiported physical volumes accessed via multiple paths. It has no effect for physical volumes without alternate paths. autoswitch option may be set to one of the following values:

y: 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.
n: 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.

-x extensibility

Set the allocation permission to add physical extents to the physical volume pv_path. extensibility can have the following values:

y: Allow allocation of additional physical extents on the physical volume. This is the default.
n: Prohibit allocation of additional physical extents on the physical volume. However, logical volumes residing on the physical volume are accessible.

-t IO_timeout

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).

-z sparepv

This option requires the installation of the optional HP MirrorDisk/UX software. It 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:

y: 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 volumes 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.
n: 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 immediately 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.

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 volume group is activated using the vgchange command (see vgchange(1M)). If the objective is to permanently add or remove a path or physical volume from the volume group, the vgextend or vgreduce commands (see vgextend(1M), and vgreduce(1M)) should instead be used.

Warning: Detaching any physical volume or path using the -a N or -a n 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 -a y options of vgchange command.

Attaching or Detaching Physical Volumes in Shared Volume Groups

The scope of the pvchange command is limited to the specific node on which it runs. Systems that are part of a Serviceguard cluster operate independently. 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 simultaneously.

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 scsimgr 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:

Only the legacy device special file naming convention is used in the volume group configuration.
The scsimgr command is used to disable the Mass Storage Subsystem multipath behavior.

EXTERNAL INFLUENCES

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

Prohibit the allocation of additional physical extents to a physical volume:

pvchange -x n /dev/dsk/c0t0d0 

Allow the allocation of additional physical extents to a physical volume:

pvchange -x y /dev/dsk/c0t0d0 

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:

pvchange -S n /dev/dsk/c0t0d0 

Switch paths whenever a better path becomes available again after a failure, even if the current path is fine:

pvchange -S y /dev/dsk/c0t0d0 

Manually switch a physical volume to use another controller path:

pvchange -s /dev/dsk/c2t0d2 

Set the IO_timeout value for a physical volume to 60 seconds:

pvchange -t 60 /dev/dsk/c2t0d2 

Set the IO_timeout value for a physical volume to zero (0) to use the driver default:

pvchange -t 0 /dev/dsk/c2t0d2 

Change the (empty) physical volume to become a stand-by spare for the volume group:

pvchange -z y /dev/dsk/c2t0d2 

Change the (active or stand-by) spare physical volume to become a regular member of the volume group:

pvchange -z n /dev/dsk/c2t0d2 

Detach a path to a physical volume

pvchange -a n /dev/dsk/c2t0d2 

Detach all the paths to a physical volume

pvchange -a N /dev/dsk/c2t0d2 

Attach a path to a physical volume

pvchange -a y /dev/dsk/c2t0d2 

The vgchange command may be used to attach all the physical volumes in a volume group and resume automatically attaching the failed physical volumes.

vgchange -a y /dev/vg_work 

WARNINGS

If the Mass Storage Subsystem multipath solution is enabled, the pvchange command options that are link specific may not stop I/Os or switch links, as they did in earlier releases. This means that pvchange -a n, pvchange -s, and pvchange -S may not stop all I/Os on a given path. The scsimgr command should be used to disable the links.