Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

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.
VxVM uses the default naming conventions of vol## for volumes and vol##-##
for plexes in a volume. For ease of administration, you can choose to select more
meaningful names for the volumes that you create.
A volume may be created under the following constraints:
■ Its name can contain up to 31 characters.
■ It can consist of up to 32 plexes, each of which contains one or more subdisks.
■ It must have at least one associated plex that has a complete copy of the data
in the volume with at least one associated subdisk.
■ All subdisks within a volume must belong to the same disk group.
You can use the Veritas Intelligent Storage Provisioning (ISP) feature to create
and administer application volumes. These volumes are very similar to the
traditional VxVM volumes that are described in this chapter. However, there are
significant differences between the functionality of the two types of volume that
prevent them from being used interchangeably.
See the Veritas Storage Foundation Intelligent Storage Provisioning Administrator’s
Guide.
Figure 1-10 shows a volume vol01 with a single plex.
Figure 1-10
Example of a volume with one plex
Volume with one plex
Plex with one subdisk
vol01
vol01-01
vol01-01
disk01-01
35Understanding Veritas Volume Manager
How VxVM handles storage management