HP-UX System Administrator's Guide: Overview

Disk Mirroring Disk mirroring writes multiple copies of data to
separate (physical or logical) devices
simultaneously.
If you are using LVM (HP’s Logical Volume
Manager), you will need to install the optional
product, MirrorDisk/UX to use disk mirroring.
MirrorDisk/UX supports up to three copies of
data if you are using LVM 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
130 System Administration Tools