HP-UX System Administrator's Guide: Overview

• SAN - Storage Area Networks (physical drives attached to a dedicated network)
• NAS - Network Attached Storage (storage attached to dedicated servers accessed
through standard network file system protocols)
Individual disk drives (whether standalone or in an array or enclosure) are often referred
to as LUNs. The term “LUN” stands for “Logical Unit”, and while it is often associated
with a physical disk drive (drive unit) within a larger array device, LUNs can point to
other (logically defined) subsets of a larger device.
Volume Managers
Physical disk drives can be used in a standalone mode; that is, they can be partitioned,
formatted with a file system, used for paging, or used by database applications as units
of storage. However, physical disk drives are usually grouped into larger pools of space
that can then be divided into logical storage containers. These containers (called volumes
or logical volumes, depending on which volume manager you are using) are not
required to respect the boundaries of the physical drives in the group. That is, they can
span multiple physical devices.
Volume managers enable you to divide and allocate these pools of space into logical
storage containers.
The pools of space are called volume groups in the Logical Volume Manager (LVM) and
disk groups in the VERITAS Volume Manager (VxVM).
The logical storage containers are referred to as logical volumes in LVM or simply volumes
in VxVM. To applications, file systems, and databases, these volumes appear to be
physical disks and are treated as such.
HP-UX 11i version 3 supports the following volume managers:
LVM The Logical Volume Manager (LVM) is detailed in HP-UX System Administrator’s
Guide: Logical Volume Management. LVM is the default volume manager for
HP-UX 11i.
VxVM The VERITAS Volume Manager (VxVM) has many features, some of which
are not available with LVM or MirrorDisk/UX (the companion product to LVM
that allows you to mirror data onto multiple physical disks).
The version of VxVM that ships with HP-UX is a base version containing a
subset of the features offered in the full version (which requires an additional
license). For complete information about which features are included with the
base version and the full version of VxVM see the VERITAS Volume Manager
Releases Notes corresponding to the version of the VERITAS Volume Manager
you are using.
50 Major Components of HP-UX