HP-UX System Administrator's Guide: Logical Volume Management (5900-3028, March 2013)

/dev/dsk/c5t0d0
/dev/dsk/c12t0d0 -- Boot Disk
Root: lvol1 on: /dev/dsk/c3t0d0
/dev/dsk/c4t0d0
Swap: lvol2 on: /dev/dsk/c3t0d0
/dev/dsk/c4t0d0
Dump: lvol2 on: /dev/dsk/c3t0d0
The physical volumes designated "Boot Disk" are bootable, having been initialized with mkboot
and pvcreate -B. Multiple lines for lvol1 and lvol2 indicate that the root and swap logical
volumes are being mirrored.
Logical Interface Format Area
LVM boot disks contain a Logical Interface Format (LIF) area, in which is stored a LABEL file. On
HP 9000 servers, the LIF area contains boot utilities such as the initial system loader (ISL), the
kernel boot loader (HPUX), the autoboot file (AUTO), and offline diagnostics.
The LABEL file is created and maintained by lvlnboot and lvrmboot. It contains information
about the starting point and size of boot-relevant logical volumes, including the boot file system
(/stand). Utilities can use the LABEL file to access the root, primary swap, and dump logical
volumes without actually using LVM.
Physical Volume Reserved Area
The physical volume reserved area (PVRA) contains information describing the physical volume,
such as its unique identifier, physical extent information, and pointers to other LVM structures on
the disk.
Volume Group Reserved Area
The volume group reserved area (VGRA) describes the volume group to which the disk belongs.
The information is replicated on all of the physical volumes and updated whenever a configuration
change is made. Among other data, it contains the following information:
• A list of physical volumes in the volume group, including physical volume status and size, and
a map of physical extents to logical volumes.
• A list of logical volumes in the volume group (including the status and capabilities of each
logical volume), its scheduling and allocation policies, and the number of mirror copies.
• A volume group header containing the VGID and three configurable parameters:
◦ the number of physical volumes allowed in the volume group
◦ the maximum number of logical volumes allowed in the volume group
◦ the maximum number of physical extents allowed per physical volume
Since each physical extent is recorded in the VGRA, the extent size has a direct bearing on the
size of the VGRA. In most cases, the default extent size is sufficient. However, if you encounter
problems, consider that the VGRA is a fixed size and a high-capacity physical volume might exceed
the total number of physical extents allowed. As a result, you might need to use a larger-than-default
extent size on high-capacity LVM disks. Conversely, if all LVM disks in a volume group are small,
the default number of extents might make the VGRA too large, wasting disk and memory space.
A smaller-than-default extent size or number of physical extents might be preferable. A high-capacity
physical volume might be unusable in a volume group whose extent size is small or set with a small
number of physical extents per disk.
User Data Area
The user data area is the region of the LVM disk used to store all user data, including file systems,
virtual memory system (swap), or user applications.
LVM Disk Layout 17