VERITAS Volume Manager 3.1 Administrator's Guide

Introduction to Volume Manager
Volumes and Virtual Objects
Chapter 1 31
Volumes and Virtual Objects
The connection between physical objects and Volume Manager objects is
made when you place a physical disk under Volume Manager control.
Volume Manager creates virtual objects and makes logical connections
between the objects. The virtual objects are then used by Volume
Manager to do storage management tasks.
NOTE The vxprint command displays detailed information on existing Volume
Manager objects. For additional information on the vxprint command,
see “Displaying Volume Manager Object Listings”.
A volume is a virtual disk device that appears to applications,
databases, and file systems as a physical disk. However, a volume does
not have the limitations of a physical disk. When you use Volume
Manager, applications access volumes created on Volume Manager disks
(VM Disks) rather than physical disks.
Volumes contain other virtual objects that you can use to manipulate
data within a volume. The virtual objects contained in volumes are: VM
disks, disk groups, subdisks, and plexes. Details of the virtual objects are
described in the following sections. Virtual objects and volume
manipulation of them are described in “Volumes”.
Volume Manager Disks
When you place a physical disk under Volume Manager control, a
Volume Manager disk (or VM Disk) is assigned to the physical disk. A
VM Disk is under Volume Manager control and is usually in a disk
group. Each VM disk corresponds to at least one physical disk. Volume
Manager allocates storage from a contiguous area of Volume Manager
disk space.
A VM disk typically includes a public region (allocated storage) and a
private region where Volume Manager internal configuration
information is stored.
Each VM Disk has a unique disk media name (a virtual disk name).
You can supply the disk name or allow Volume Manager to assign a