Red Hat GLOBAL FILE SYSTEM 5.0, Руководство администратора

Страница: 88 / 112

If the on-disk LVM metadata takes as least as much space as what overrode it, this command
can recover the physical volume. If what overrode the metadata went past the metadata area,
the data on the volume may have been affected. You might be able to use the
fsck
command
to recover that data.
5. Replacing a Missing Physical Volume
If a physical volume fails or otherwise needs to be replaced, you can label a new physical
volume to replace the one that has been lost in the existing volume group by following the same
procedure as you would for recovering physical volume metadata, described in Section 4,
“Recovering Physical Volume Metadata” . You can use the
--partial
and
--verbose
arguments of the
vgdisplay
command to display the UUIDs and sizes of any physical volumes
that are no longer present. If you wish to substitute another physical volume of the same size,
you can use the
pvcreate
command with the
--restorefile
and
--uuid
arguments to
initialize a new device with the same UUID as the missing physical volume. You can then use
the
vgcfgrestore
command to restore the volume group's metadata.
6. Removing Lost Physical Volumes from a Volume
Group
If you lose a physical volume, you can activate the remaining physical volumes in the volume
group with the
--partial
argument of the
vgchange
command. You can remove all the logical
volumes that used that physical volume from the volume group with the
--removemissing
argument of the
vgreduce
command.
It is recommended that you run the
vgreduce
command with the
--test
argument to verify
what you will be destroying.
Like most LVM operations, the
vgreduce
command is reversible in a sense if you immediately
use the
vgcfgrestore
command to restore the volume group metadata to its previous state.
For example, if you used the
--removemissing
argument of the
vgreduce
command without
the
--test
argument and find you have removed logical volumes you wanted to keep, you can
still replace the physical volume and use another
vgcfgrestore
command to return the volume
group to its previous state.
7. Insufficient Free Extents for a Logical Volume
You may get the error message "Insufficient free extents" when creating a logical volume when
you think you have enough extents based on the output of the
vgdisplay
or
vgs
commands.
This is because these commands round figures to 2 decimal places to provide human-readable
output. To specify exact size, use free physical extent count instead of some multiple of bytes to
determine the size of the logical volume.
The
vgdisplay
command, by default, includes this line of output that indicates the free physical
extents.
Chapter 6. LVM Troubleshooting
76