Veritas Volume Manager 5.1 SP1 Administrator"s Guide (5900-1506, April 2011)

See “VM disks” on page 30.
In releases before VxVM 4.0, the default disk group was rootdg (the root disk
group). For VxVM to function, the rootdg disk group had to exist and it had to
contain at least one disk. This requirement no longer exists, and VxVM can work
without any disk groups configured (although you must set up at least one disk
group before you can create any volumes of other VxVM objects).
See “System-wide reserved disk groups” on page 210.
You can create additional disk groups when you need them. 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.
See “Reorganizing the contents of disk groups” on page 250.
Volumes are created within a disk group. A given volume and its plexes and
subdisks 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 small 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 takes the form diskgroup##, where diskgroup is the name of the disk group
to which the disk belongs.
See “Disk groups” on page 29.
Figure 1-6 shows a VM disk with a media name of disk01 that is assigned to the
physical disk, devname.
Understanding Veritas Volume Manager
How VxVM handles storage management
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