HP-UX System Administrator's Guide: Logical Volume Management (762803-001, March 2014)

crw-r----- 1 root root 64 0x010001 Mar 28 2004 rlvol1
crw-r----- 1 root root 64 0x010002 Mar 28 2004 rlvol2
By default, volume group numbering begins with zero (vg00), while logical volumes begin with
one (lvol1). This is because the logical volume number corresponds to the minor number and the
volume group's group file is assigned minor number 0.
Physical volumes use the device files associated with their disk. LVM does not create device files
for physical volumes.
1.5.4.1 Version 1.0 Device Number Format
Table 2 lists the format of the device file number for Version 1.0 volume groups.
Table 2 Version 1.0 Device Number Format
Logical Volume
Number
ReservedVolume Group
Number
Major Number
0–0xff
0=group file
00–0xff64
For Version 1.0 volume groups, the major number for LVM device files is 64. The volume group
number is encoded into the top eight bits of the minor number, and the logical volume number is
encoded into the low eight bits. Logical volume number 0 is reserved for the group file.
1.5.4.2 Version 2.x Device Number Format
Table 3 lists the format of the device file number for Version 2.x volume groups.
Table 3 Version 2.x Device Number Format
Logical Volume NumberVolume Group NumberMajor Number
0–0x7ff
0=group file
0–0x7ff128
For Version 2.x volume groups, the major number for LVM device files is 128. The volume group
number is encoded into the top twelve bits of the minor number, and the logical volume number
is encoded into the low twelve bits. Logical volume number 0 is reserved for the group file.
NOTE: The most significant bit of the volume group number and logical volume number fields
are reserved and must be zero.
The device number format is subject to change.
1.6 LVM Disk Layout
NOTE: This information applies only to disks belonging to Version 1.0 and Version 2.2 (or higher)
volume groups.
There are two kinds of LVM disk layouts, one for boot disks and another for all other LVM disks.
These differ in their data structures. Nonbootable disks have two reserved areas: the physical
volume reserved area (PVRA) and the volume group reserved area (VGRA). Bootable disks have
a PVRA and VGRA, and additional sectors reserved for the boot data reserved area (BDRA) and
boot LIF.
1.6.1 Boot Data Reserved Area
The BDRA contains the information needed to configure the root, primary swap, and dump logical
volumes, and to mount the root file system.
1.6 LVM Disk Layout 19