Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Administering a System: Managing Disks and Files
Managing Disks
Chapter 6 589
Detaching one or more links to a physical volume will not necessarily
cause LVM to stop using that physical volume entirely. If the detached
link is the primary path to the device, LVM will begin using any
available alternate link to it. LVM will only stop using the physical
volume when all the links to it are detached.
If all the links to a device are detached, the associated physical volume
will be unavailable to the volume group. The links remain associated
with the volume group but no I/O requests will be queued to it by LVM
until it is reattached. This means that the data on that physical volume
will be temporarily unavailable; consequently, you as the adminstrator
must make sure that any availability requirements for that data can be
satisfied, by mirroring if necessary, before you make the device
unavailable by detaching it.
Detaching a link does not disable sparing. That is, if all links to a
physical volume are detached, and a suitable spare physical volume is
available in the volume group, LVM will use it to reconstruct the
detached disk. For more information on sparing, see “Maintaining High
Availability in the Event of Disk Failure” on page 640.
You can view the status of all links to a physical volume using vgdisplay
with the -v option.
Restoring a Detached Link to a Physical Volume
Restoring a detached link to a physical volume, or reattaching it,
makes that link available to the volume group. LVM may begin using
that link as necessary to access the disk.
To reattach a specific path to a physical volume, use the pvchange
command with the -a option. For example, enter:
pvchange -a y /dev/dsk/c5t0d0
Because detaching a link to a physical volume is meant to be temporary,
all detached links in a volume group are reattached when the volume
group is activated, either at boot time or with an explicit vgchange
command, such as:
vgchange -a y /dev/vg02
Setting Up Disk Striping
When you use disk striping, you create a logical volume that spans
multiple disks, allowing successive blocks of data to go to logical extents
on different disks. For example, a three-way striped logical volume has