HP-UX System Administrator's Guide: Overview HP-UX 11i v3 (B3921-90011, September 2010)

Table 3-2 Storage Components and how they are Addressed
How it is addressedStack Component
Once created, a file system is usually addressed by its mount point, the directory in the
HP-UX directory tree that represents the root of the files in that file system.
File System
Not all logical / physical volumes contain file systems. Other uses of these volumes
include:
• swap space
• dump space
• database managed space
Swap and dump space are managed by the kernel, and database managed space is
usually managed by the database application.
RAW access
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
The first two items in the list above are determined by the major number of a device special file,
the latter two items are determined by the minor number of a device special file.
52 Major Components of HP-UX