VERITAS Volume Manager 4.1 Administrator's Guide

Chapter 4 156
Creating a 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. Examples of
this are:
• 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.
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 allows you to move only the application or user data that should be
moved.
Disks must be placed in disk groups before VxVM can use the disks for
volumes. VxVM always requires the rootdg disk group to be defined, but
you can add more disk groups as required.
NOTE VxVM commands create all volumes in the default disk group, rootdg, if
no alternative disk group is specified using the -g option (see “Specifying
a Disk Group to Commands” on page 153). All commands default to the
rootdg disk group unless the disk group can be deduced from other
information such as a disk name.
A disk group must have at least one disk associated with it. A new disk
group can be created when you use menu item 1 (Add or initialize one or
more disks) of the vxdiskadm command to add disks to VxVM control, as
described in “Adding a Disk to VxVM” on page 83. Disks to be added to a
disk group must not already belong to an existing disk group.
You can also use the vxdiskadd command to create a new disk group, for
example:
# vxdiskadd c1t1d0
where c1t1d0 is the device name of a disk that is not currently assigned
to a disk group.
Disk groups can also be created by using the command vxdg init:
# vxdg init diskgroup diskname=devicename
For example, to create a disk group named mktdg on device c1t0d0:
# vxdg init mktdg mktdg01=c1t0d0