VERITAS Volume Manager 3.1 Storage Administrator Administrator's Guide

Volume Tasks
Creating a Volume
Chapter 4150
Note that RAID-5 volumes cannot be mirrored.
• Mirrored Volume
Volumes with concatenated or striped layouts can be mirrored to
increase data availability. All of the data in a mirrored volume is
duplicated on at least one other physical disk. If one of the disks fails,
the data can still be accessed from one of the remaining disks.
The plexes in a mirrored volume typically have the same layout, but a
volume can consist of plexes with different layouts. A mirrored
volume has a “mixed” layout if the plexes in the volume have different
layouts.
• Layered Volume
A layered volume is built on one or more other volumes. The
underlying volumes are typically mirrored. In layered volumes,
mirroring is done at a lower level and with smaller granularity than
with non-layered volumes, so each mirror covers a relatively small
storage region.
Layered volumes tolerate disk failure better than non-layered
volumes and provide improved data redundancy. If a disk in a layered
volume fails, only a portion of the redundancy is lost and recovery
time is usually quicker than it would be for a non-layered volume.
Layered volumes also reduce the chance that two disk failures will
result in lost data.
The underlying volumes in a layered volume are used exclusively by
the Volume Manager and are not intended for user manipulation.
With the Storage Administrator, you can create the following types of
layered volumes:
— Concatenated Pro Volume
A concatenated pro volume is a layered concatenated volume that
is mirrored.
— Striped Pro Volume
A striped pro volume is a layered striped volume that is mirrored.
The following table summarizes the advantages and disadvantages of