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

with Version 1 volume groups, and up to six copies of data
if you are using LVM with Version 2 volume groups.
If you are using the VERITAS Volume Manager, the ability
to mirror your root volume group is built in to the base
product. By licensing the full version of the VERITAS
Volume Manager, you gain the ability to mirror all your
volume groups, up to 32 copies of the data.
RAIDs and Surestore Disk Arrays Data redundancy can also be accomplished at the hardware
level. RAIDs (redundant arrays of inexpensive disks) and
HP Surestore Disk Arrays have the capability to make
multiple copies of data written to them, and some even
have multiple controllers for redundancy of access should
a controller fail.
NOTE: RAID levels that include parity disks are able to
reconstruct lost data on the fly until a failed disk is repaired
or replaced. This is almost as good as multiple copies of
the data, however for exceptionally important data, be
exceptionally safe by having a copy of the data.
Protecting Against Hardware Failure
Depending on the specific hardware you have (server types, storage devices, and so on), HP-UX
11i version 3 offers numerous ways of protecting your computing operations against hardware
failure. Here are some key features to consider:
Serviceguard For mission critical installations, Serviceguard takes
redundancy an extra step by having multiple servers
connected to external disks or arrays. If one server fails,
Serviceguard can switch to a stand-by server capable of
carrying on the functions of the failed server while the
original is repaired.
Persistent Device Special Files HP-UX 11i version 3 introduces a new type of device
special file called a persistent device special file. Unlike legacy
device special files
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that address devices by the hardware
path to them, persistent device special files use unique
identifiers built into (or associated with) supported devices to
address them. This means that multiple hardware paths
can be used to address the same device, preventing single
points of failure in interface cards/slots.
Online Addition and Replacement Online Addition, Replacement, and Deletion (OL*) is an
HP-UX feature that allows for the addition, replacement,
and deletion of PCI / PCI-X cards (adapters) while a system
is running (without requiring a reboot).
This feature enhances overall high-availability since the
system can remain active while an I/O adapter is being
added or replaced. When combined with other
high-availability products, such as Serviceguard, system
availability is significantly improved.
Failed devices that support PCI OL*, if not critical to your
operation, can be replaced or removed.
10. Legacy device special files are still supported in HP-UX 11i version 3 and can be used in conjunction with persistent
device special files.
106 System Administration Tools