Dynamic Root Disk and MirrorDisk/UX

Introduction
System administrators frequently use MirrorDisk/UX to create a redundant copy of an HP-UX system
as protection against hardware failures. HP’s Dynamic Root Disk (DRD), alternatively, provides a
means of protecting against software failures — changes can be staged on an inactive copy of the
system and an unchanged copy can be retained for recovery.
Because a DRD clone or patched clone will become a booted system, it is desirable to mirror the
clone as well. Depending on the number of available disks and policies about use of the storage in
the Storage Area Network (SAN), DRD users can:
• Mirror their clone when it is created.
• Mirror it after creation but before boot.
• Mirror it after the clone is booted.
Some data centers always boot from internal disks on a system; others use SAN disks for mirrors or
DRD clones. This document describes the various mirroring strategies a system administrator can use
for combining the benefits of DRD clones and LVM mirrors.
The scenarios below describe strategies that a system administrator might use in four-disk, three-disk,
and two-disk environments.
Four Disk Scenario – Mirroring the Clone When it is
Created
In this scenario, the four disks are the boot disk, the boot mirror, the clone disk, and the clone mirror.
To apply this scenario, a system administrator needs to have the following resources available:
• A licensed copy of MirrorDisk/UX
One way to determine if you have a licensed copy of MirrorDisk/UX is to execute the
following command:
# /usr/sbin/lvextend -?
If the usage statement displays the following option, then you have access to
MirrorDisk/UX:
-m MirrorCopies
Alternatively, you can check for the LVM.LVM-MIRROR-RUN fileset with the following
command:
# /usr/sbin/swlist –l fileset LVM.LVM-MIRROR-RUN
If you do not have access to MirrorDisk/UX and want to mirror a DRD clone, you need to
license MirrorDisk/UX. (This release of DRD does not support mirroring of VxVM
volumes.) This product is available either through several of the Operating Environments
(including the Mission Critical Operating Environment) as well as from the bundle
B2491BA. To obtain a license and a copy of the software, contact your HP support
representative or search for “MirrorDisk” at
http://software.hp.com/.