Figure 2 Physical Extents and Logical Extents
As shown in
Figure 2
, the contents of the first logical volume are contained on all three physical
volumes in the volume group. Because the second logical volume is mirrored, each logical extent
is mapped to more than one physical extent. In this case, there are two physical extents containing
the data, each on both the second and third disks within the volume group.
By default, LVM assigns physical extents to logical volumes by selecting available physical extents
from disks in the order in which they appear in the LVM configuration files,
/etc/lvmtab
and
/etc/lvmtab_p
. As a system administrator, you can bypass this default assignment and control
which disks are used by a logical volume (see
“Extending a Logical Volume to a Specific Disk”
(page 54)
).
If a logical volume is to be used for root, boot, primary swap, or dump, the physical extents must
be
contiguous
, which means that the physical extents must be allocated in increasing order with
no gaps on a single physical volume. For logical volumes that are not being used for root, boot,
primary swap or dump, physical extents that correspond to contiguous logical extents within a
logical volume can be
noncontiguous
on a physical volume or reside on entirely different disks.
As a result, a file system created within one logical volume can reside on more than one disk.
LVM Volume Group Versions
As of the March 2010 release of HP-UX 11i Version 3, LVM supports four versions of volume
groups. All information and tasks in this document apply to all volume group versions except where
noted.
Version 1.0 is the version supported on all current and previous versions of HP-UX 11i. The
procedures and command syntax for managing Version 1.0 volume groups are unchanged from
previous releases. When creating a new volume group,
vgcreate
defaults to Version 1.0.
LVM Volume Group Versions
11
