VERITAS Volume Manager 4.1 Administrator's Guide

Understanding VERITAS Volume Manager
How VxVM Handles Storage Management
Chapter 1 13
NOTE Even though rootdg is the default disk group, it does not necessarily
contain the root disk. In the current release, the root disk may be under
VxVM or LVM control.
You can create additional disk groups as necessary. Disk groups allow
you to group disks into logical collections. A disk group and its
components can be moved as a unit from one host machine to another.
The ability to move whole volumes and disks between disk groups, to
split whole volumes and disks between disk groups, and to join disk
groups is described in “Reorganizing the Contents of Disk Groups” on
page 172.
Volumes are created within a disk group. A given volume must be
configured from disks in the same disk group.
VM Disks
When you place a physical disk under VxVM control, a VM disk is
assigned to the physical disk. A VM disk is under VxVM control and is
usually in a disk group. Each VM disk corresponds to one physical disk.
VxVM allocates storage from a contiguous area of VxVM disk space.
A VM disk typically includes a public region (allocated storage) and a
private region where VxVM internal configuration information is stored.
Each VM disk has a unique disk media name (a virtual disk name). You
can either define a disk name of up to 31 characters, or allow VxVM to
assign a default name that typically takes the form disk##. Figure 1-6,
“VM Disk Example,” shows a VM disk with a media name of disk01 that
is assigned to the physical disk devname.
Figure 1-6 VM Disk Example
disk01
devname
VM DiskPhysical Disk