Handling Size Decreases
CAUTION:
A similar procedure can also be used when the size of a physical volume is decreased.
However, there are limitations:
•
Sequence:
The sequence must be reversed to avoid data corruption.
For an increase in size, the sequence is:
1.
Increase the LUN size from the array side.
2.
Then, increase the volume group size from the LVM side.
For a decrease in size, the sequence is:
1.
Decrease the volume group size from the LVM side.
2.
Then, decrease the LUN size from the array side.
•
Volume Group Status
Prior to the March 2009 Update,
vgmodify
for handling LUN contraction was only supported
on Version 1.0 volume groups, and the volume group had to be deactivated before attempting
any reduction. If you reduce the size of the LUN while the volume group was activated, LVM
would mark the physical volume as unavailable.
Beginning with the March 2009 Update,
vgmodify
for handling LUN contraction can now
be performed on Version 1.0 or Version 2.x volume groups and the volume group can be
activated (this is known as Dynamic LUN Contraction, or DLC). For an active volume group,
you can use the
–C
and
–a
options of
vgmodify
to recognize and accommodate size
decreases without deactivating the volume group. For more information, see vgmodify(1M).
•
Physical Extent Quantity
If the physical volume has any allocated physical extents beyond the target size,
vgmodify
prints an error message and exits without changing the physical volume. In this case, you must
be prepared to restore the LUN to its original size (ensuring the same disk space is allocated).
Supported LUN Changes per Release
This table shows what is supported with regards to whether the volume group needs to be
deactivated for LUN size changes:
Table 8 Supported LUN Changes Per Release
LUN Size Decrease
LUN Size Increase
Not supported
Volume group must be deactivated; only
Version 1.0 volume groups supported.
Prior to September 2008
Update
Not supported
Volume group can be either deactivated or
active (use
vgmodify–E–a
); only Version
1.0 volume group supported.
Beginning with the
September 2008 Update
Volume group can be either deactivated or
active (use
vgmodify–C–a
); Version 1.0
and 2.x volume groups supported
Volume group can be either deactivated or
active (use
vgmodify–E–a
); Version 1.0
and Version 2.x volume groups supported.
Beginning with the
March 2009 Update
Changing Physical Volume Boot Types
NOTE:
Version 2.0 and 2.1 volume groups do not support bootable physical volumes.
When a physical volume is initialized for LVM use, it can be made bootable or nonbootable.
Bootable physical volumes require additional space in their LVM metadata for boot utilities and
84
Administering LVM
