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.
Figure: Example of a volume with one plex shows a volume vol01 with a single plex.
The volume vol01 has the following characteristics:
It contains one plex named vol01-01.
The plex contains one subdisk named disk01-01.
The subdisk disk01-01 is allocated from VM disk disk01.
Figure: Example of a volume with two plexes shows a mirrored volume vol06 with two data plexes.
Each plex of the mirror contains a complete copy of the volume data.
The volume vol06 has the following characteristics:
It contains two plexes named vol06-01 and vol06-02.
Each plex contains one subdisk.
Each subdisk is allocated from a different VM disk (disk01 and disk02).
VxVM supports the concept of layered volumes in which subdisks can contain volumes.