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

continues to refer to it. You can replace disks by first associating a different
physical disk with the name of the disk to be replaced and then recovering any
volume data that was stored on the original disk (from mirrors or backup copies).
Having disk groups that contain many disks and VxVM objects causes the private
region to fill. If you have large disk groups that are expected to contain more than
several hundred disks and VxVM objects, you should set up disks with larger
private areas. A major portion of a private region provides space for a disk group
configuration database that contains records for each VxVM object in that disk
group. Because each configuration record is approximately 256 bytes, you can
use the configuration database copy size to estimate the number of records that
you can create in a disk group. You can obtain the copy size in blocks from the
output of the vxdg list diskgroup command. It is the value of the permlen
parameter on the line starting with the string “config:”. This value is the smallest
of the len values for all copies of the configuration database in the disk group.
The value of the free parameter indicates the amount of remaining free space in
the configuration database.
See “Displaying disk group information” on page 216.
One way to overcome the problem of running out of free space is to split the
affected disk group into two separate disk groups.
See “Reorganizing the contents of disk groups” on page 250.
See “Backing up and restoring disk group configuration data” on page 266.
Before Veritas Volume Manager (VxVM) 4.0, a system installed with VxVM was
configured with a default disk group, rootdg. This group had to contain at least
one disk. By default, operations were directed to the rootdg disk group. From
release 4.0 onward, VxVM can function without any disk group having been
configured. Only when the first disk is placed under VxVM control must a disk
group be configured. Now, you do not have to name any disk group rootdg. If you
name a disk group rootdg, it has no special properties because of this name.
See “Specification of disk groups to commands” on page 210.
Note: Most VxVM commands require superuser or equivalent privileges.
Additionally, before VxVM 4.0, some commands such as vxdisk were able to
deduce the disk group if the name of an object was uniquely defined in one disk
group among all the imported disk groups. Resolution of a disk group in this way
is no longer supported for any command.
209Creating and administering disk groups
About disk groups