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

• DLT tape drives / libraries
• Magneto-optical drives / libraries
• DDS tapes
Disk drives can be:
• Individual drives
• Drive enclosures (groups of multiple disk drives that are treated as individual drives)
• Disk Arrays (like drive enclosures but with an added disk controller for local intelligence
in managing the contained storage (for example, RAIDs)
• 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.
NOTE: The pools of space are called volume groups in the Logical Volume Manager and disk
groups in the VERITAS Volume Manager.
Both volume managers can co-exist on a server. Each volume manager keeps track of which
disks it is controlling and any given physical disk can only be a controlled by one volume manager
at a time. The utility vxvmconvert can convert an LVM physical volume to a VxVM disk if you
want to migrate a disk from LVM to VxVM for greater configuration flexibility.
44 Major Components of HP-UX