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

Administering a System: Managing Disks and Files
Managing File Systems
Chapter 6640
Step 7. Run vgchange -a y to reactivate the volume group to which the disk
belongs. Since the volume group is already currently active, no automatic
synchronization occurs:
vgchange -a y /dev/ vol_group
Step 8. If any of the logical volumes on the disk had a nondefault timeout
assigned, restore the previous timeout:
lvchange -t value /dev/ vol_group /lvol n
Step 9. Now run vgsync to manually synchronize all the extents in the volume
group:
vgsync /dev/ vol_group
Consult the HP-UX Reference for additional information on any of the
above commands.
NOTE You can use the same procedure to replace a disk that contains
unmirrored logical volumes. However, by removing the disk, you will
permanently lose any unmirrored data on that disk. Therefore, before
starting this procedure, confirm that you have a backup of any
unmirrored logical volume, then halt any applications using it, and
unmount any file system mounted on it. After replacing the disk and
activating the volume group, do not use those unmirrored logical
volumes until you have recovered them from backup.
Maintaining High Availability in the Event of Disk Failure
Normally, if a mirrored disk fails, in order to maintain mirroring you will
need to immediately deactivate its volume group and follow the steps
above to replace the disk. During this interval, your file system will be
unavailable and your data will not have an extra mirrored copy unless
you set up double mirroring. Even with double mirroring, your level of
safety will be reduced due to the loss of one of your two mirror copies.
To prevent this possibility, you can use one or more spare disks within
each of your volume groups to serve as substitute devices in the event of
disk failure. Once you have done this, LVM will automatically
“reconfigure” the volume group so that the spare physical volume will
take the place of a failed device without any intervention required. That
is, a copy of the data from all the logical volumes currently on the failed