VERITAS Volume Manager 4.1 Administrator's Guide

Understanding VERITAS Volume Manager
How VxVM Handles Storage Management
Chapter 1 15
Plexes
VxVM uses subdisks to build virtual objects called plexes. A plex consists
of one or more subdisks located on one or more physical disks. For
example, see the plex vol01-01 shown in Figure 1-9, “Example of a Plex
with Two Subdisks,”
Figure 1-9 Example of a Plex with Two Subdisks
You can organize data on subdisks to form a plex by using the following
methods:
• concatenation
• striping (RAID-0)
• mirroring (RAID-1)
• striping with parity (RAID-5)
Concatenation, striping (RAID-0), mirroring (RAID-1) and RAID-5 are
described in “Volume Layouts in VxVM” on page 18.
Volumes
A volume is a virtual disk device that appears to applications, databases,
and file systems like a physical disk device, but does not have the
physical limitations of a physical disk device. A volume consists of one or
more plexes, each holding a copy of the selected data in the volume. Due
to its virtual nature, a volume is not restricted to a particular disk or a
specific area of a disk. The configuration of a volume can be changed by
using VxVM user interfaces. Configuration changes can be accomplished
without causing disruption to applications or file systems that are using
the volume. For example, a volume can be mirrored on separate disks or
moved to use different disk storage.
disk01
vol01-01
disk01-01
disk01-02
disk01-01
disk01-02
Plex
Subdisks