HP-UX System Administrator's Guide: Overview

Table 3-2 Storage Components and how they are Addressed (continued)
How it is addressedStack Component
The logical containers allocated from space in a volume group or disk group
are addressed by their volume name. Because these volumes are disk drives
from the perspective of the operating system, they have associated device
files.
LVM logical volumes have device files with names of the form:
• /dev/vgxx/lvoln
• /dev/vgxx/rlvoln
where xx represents the volume group that the logical volume belongs to,
and n represents the logical volume number within that volume group. The
directory lvoln contains the block device special files and the directory
rlvoln contains the character device special files.
VxVM volumes have device files with names of the form:
• /dev/vx/dsk/diskgroupname/volnn
• /dev/vx/rdsk/diskgroupname/volnn
where diskgroupname is the name assigned to the volume group associated
with the device files and nn represents the volume number.
(Logical) Volumes
LVM Volume Groups have names, usually of the form “vgnn” (where nn
represents the volume group number). The volume group that contains the
root file system (if the root file system is contained in an LVM logical volume)
is vg00.
If you are using the VERITAS Volume Manager (and your root file system is
contained in a VxVM volume), the root VxVM disk group is usually called
rootdg
1
.
Volume / Disk Groups
The fundamental building blocks of both LVM Volume Groups and VxVM
Disk Groups are physical disk drives.
Physical Disks
1 In releases of VERITAS Volume Manager (VxVM) prior to release 4.0, a system installed with VxVM
was configured with a default disk group, rootdg, that had to contain at least one disk. By default,
operations were directed to the rootdg disk group. Beginning with VxVM release 4.0, VxVM can function
with no disk groups configured. There is no longer a requirement that you name any disk group rootdg,
and any disk group that is named rootdg has no special properties because of that name.
Device Special Files
HP-UX, applications, and other processes communicate with devices and pseudo-devices
by writing to and reading from device special files. Device special files are in a special
format that tells HP-UX:
• Whether to communicate with the device using character or block transmissions
• Which device driver to use when communicating with the associated device
• How to locate/identify the device
• Any driver-specific attributes needed for communicating with a device
60 Major Components of HP-UX