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

■ Upgrading the disk group version
■ About the configuration daemon in VxVM
■ Backing up and restoring disk group configuration data
■ Using vxnotify to monitor configuration changes
■ Working with existing ISP disk groups
About disk groups
Disk groups are named collections of disks that share a common configuration.
Volumes are created within a disk group and are restricted to using disks within
that disk group.
Data related to a particular set of applications or a particular group of users may
need to be made accessible on another system. These situations include the
following:
■ A system has failed and its data needs to be moved to other systems.
■ The work load must be balanced across a number of systems.
You must place disks in one or more disk groups before VxVM can use the disks
for volumes. It is important that you locate data related to particular applications
or users on an identifiable set of disks. When you need to move these disks, this
lets you move only the application or user data that should be moved. The disk
group also provides a single object to move, rather than specifying all objects
within the disk group individually.
As system administrator, you can create additional disk groups to arrange your
system’s disks for different purposes. Many systems only use one disk group,
unless they have a large number of disks. You can initialize, reserve, and add disks
to disk groups at any time. You do not have to add disks to disk groups until the
disks are needed to create VxVM objects.
Veritas Volume Manager's Cross-platform Data Sharing (CDS) feature lets you
move VxVM disks and objects between machines that are running under different
operating systems. Disk groups may be made compatible with CDS.
For more information about CDS, see the Veritas Storage Foundation Advanced
Features Administrator’s Guide.
When you add a disk to a disk group, you name that disk (for example, mydg02).
This name identifies a disk for operations such as creating or mirroring a volume.
The name also relates directly to the underlying physical disk. If a physical disk
is moved to a different target address or to a different controller, the name mydg02
Creating and administering disk groups
About disk groups
208